# POST /api/invoicing/custom-field-definitions

Custom Field Definitions: Creates a new invoice custom field definition.

A biller holds at most 20 definitions, active and inactive alike. Deactivating a definition
does not free a slot; deleting one does. The key is unique per biller, compared
case-insensitively: `po_number` and `PO_Number` are the same key. Inactive
definitions hold their key; a deleted definition's key can be reused. The key cannot be
changed after creation.

**Operation ID:** `invoiceCustomFieldDefinitionCreate`

## Authorization

Requires: Invoicing.CustomFieldDefinitions, Invoicing.CustomFieldDefinitions.Create, merchant scope.

Requires API key scope: `admin`

Required permissions:
- `Invoicing.CustomFieldDefinitions`
- `Invoicing.CustomFieldDefinitions.Create`

## Parameters

| Name | In | Required | Type | Description |
| --- | --- | --- | --- | --- |
| suppressNulls | query | no | boolean | If true, omit properties with null values. |

## Request Body

**Content type:** `application/json`

Schema: [`InvoiceCustomFieldDefinitionCreateDto`](https://devportal.demo.winkpg.io/docs/api/models/InvoiceCustomFieldDefinitionCreateDto.md)

Properties:
- `label` (string) required: (nullable, max length 200)
- `description` (string): Conditional: When Description is not null. Max length: 2000. (nullable)
- `isRequired` (boolean): (nullable)
- `isActive` (boolean): (nullable)
- `sortOrder` (integer(int32)): Conditional: When SortOrder is not null. Must be >= 0. (nullable)
- `options` (array<string>): For `Dropdown` fields, the list of selectable options. (nullable)
- `maxLength` (integer(int32)): Maximum length for `Text` fields. Conditional: When MaxLength is not null. Must be > 0. (nullable)
- `regexPattern` (string): Regex validation pattern for `Text` fields. Conditional: When RegexPattern is not null. Max length: 2000. (nullable)
- `regexErrorMessage` (string): Error message when regex validation fails. Conditional: When RegexErrorMessage is not null. Max length: 2000. (nullable)
- `billerId` (string(uuid)) required
- `billerType` ([InvoicePartyType](https://devportal.demo.winkpg.io/docs/api/models/InvoicePartyType.md)): Identifies the type of entity acting as the biller or recipient on an invoice.
  Values:
  - `GatewayOwner`: Platform-level gateway owner.
  - `Reseller`: Reseller entity.
  - `Merchant`: Merchant entity.
  - `Customer`: End customer.
- `key` (string) required: (nullable, max length 100)
- `fieldType` ([CustomFieldType](https://devportal.demo.winkpg.io/docs/api/models/CustomFieldType.md)): The data type of a custom field definition.
  Values:
  - `Text`
  - `Dropdown`
  - `Checkbox`
  - `Date`
  - `Numeric`

_Example: Required purchase order number_

Defines a text field every new invoice from the merchant must carry: an invoice create with no value for it, or an update whose customFields leave it out, answers 400 Invoicing:CustomField:Required, and a value that is longer than 20 characters or does not match the pattern answers 400 Invoicing:CustomField:InvalidValue with the error message given here. The key is fixed once created and unique per merchant, compared without regard to case: a duplicate answers 409 Invoicing:CustomFieldDefinition:KeyAlreadyExists. A merchant holds at most 20 definitions, active or inactive. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer's purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}
```

_Example: Optional department dropdown_

Defines an optional dropdown. A value sent on an invoice must match one of the options exactly, or the request answers 400 Invoicing:CustomField:InvalidValue. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}
```

**Content type:** `text/json`

Schema: [`InvoiceCustomFieldDefinitionCreateDto`](https://devportal.demo.winkpg.io/docs/api/models/InvoiceCustomFieldDefinitionCreateDto.md)

Properties:
- `label` (string) required: (nullable, max length 200)
- `description` (string): Conditional: When Description is not null. Max length: 2000. (nullable)
- `isRequired` (boolean): (nullable)
- `isActive` (boolean): (nullable)
- `sortOrder` (integer(int32)): Conditional: When SortOrder is not null. Must be >= 0. (nullable)
- `options` (array<string>): For `Dropdown` fields, the list of selectable options. (nullable)
- `maxLength` (integer(int32)): Maximum length for `Text` fields. Conditional: When MaxLength is not null. Must be > 0. (nullable)
- `regexPattern` (string): Regex validation pattern for `Text` fields. Conditional: When RegexPattern is not null. Max length: 2000. (nullable)
- `regexErrorMessage` (string): Error message when regex validation fails. Conditional: When RegexErrorMessage is not null. Max length: 2000. (nullable)
- `billerId` (string(uuid)) required
- `billerType` ([InvoicePartyType](https://devportal.demo.winkpg.io/docs/api/models/InvoicePartyType.md)): Identifies the type of entity acting as the biller or recipient on an invoice.
  Values:
  - `GatewayOwner`: Platform-level gateway owner.
  - `Reseller`: Reseller entity.
  - `Merchant`: Merchant entity.
  - `Customer`: End customer.
- `key` (string) required: (nullable, max length 100)
- `fieldType` ([CustomFieldType](https://devportal.demo.winkpg.io/docs/api/models/CustomFieldType.md)): The data type of a custom field definition.
  Values:
  - `Text`
  - `Dropdown`
  - `Checkbox`
  - `Date`
  - `Numeric`

_Example: Required purchase order number_

Defines a text field every new invoice from the merchant must carry: an invoice create with no value for it, or an update whose customFields leave it out, answers 400 Invoicing:CustomField:Required, and a value that is longer than 20 characters or does not match the pattern answers 400 Invoicing:CustomField:InvalidValue with the error message given here. The key is fixed once created and unique per merchant, compared without regard to case: a duplicate answers 409 Invoicing:CustomFieldDefinition:KeyAlreadyExists. A merchant holds at most 20 definitions, active or inactive. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer's purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}
```

_Example: Optional department dropdown_

Defines an optional dropdown. A value sent on an invoice must match one of the options exactly, or the request answers 400 Invoicing:CustomField:InvalidValue. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}
```

**Content type:** `application/*+json`

Schema: [`InvoiceCustomFieldDefinitionCreateDto`](https://devportal.demo.winkpg.io/docs/api/models/InvoiceCustomFieldDefinitionCreateDto.md)

Properties:
- `label` (string) required: (nullable, max length 200)
- `description` (string): Conditional: When Description is not null. Max length: 2000. (nullable)
- `isRequired` (boolean): (nullable)
- `isActive` (boolean): (nullable)
- `sortOrder` (integer(int32)): Conditional: When SortOrder is not null. Must be >= 0. (nullable)
- `options` (array<string>): For `Dropdown` fields, the list of selectable options. (nullable)
- `maxLength` (integer(int32)): Maximum length for `Text` fields. Conditional: When MaxLength is not null. Must be > 0. (nullable)
- `regexPattern` (string): Regex validation pattern for `Text` fields. Conditional: When RegexPattern is not null. Max length: 2000. (nullable)
- `regexErrorMessage` (string): Error message when regex validation fails. Conditional: When RegexErrorMessage is not null. Max length: 2000. (nullable)
- `billerId` (string(uuid)) required
- `billerType` ([InvoicePartyType](https://devportal.demo.winkpg.io/docs/api/models/InvoicePartyType.md)): Identifies the type of entity acting as the biller or recipient on an invoice.
  Values:
  - `GatewayOwner`: Platform-level gateway owner.
  - `Reseller`: Reseller entity.
  - `Merchant`: Merchant entity.
  - `Customer`: End customer.
- `key` (string) required: (nullable, max length 100)
- `fieldType` ([CustomFieldType](https://devportal.demo.winkpg.io/docs/api/models/CustomFieldType.md)): The data type of a custom field definition.
  Values:
  - `Text`
  - `Dropdown`
  - `Checkbox`
  - `Date`
  - `Numeric`

_Example: Required purchase order number_

Defines a text field every new invoice from the merchant must carry: an invoice create with no value for it, or an update whose customFields leave it out, answers 400 Invoicing:CustomField:Required, and a value that is longer than 20 characters or does not match the pattern answers 400 Invoicing:CustomField:InvalidValue with the error message given here. The key is fixed once created and unique per merchant, compared without regard to case: a duplicate answers 409 Invoicing:CustomFieldDefinition:KeyAlreadyExists. A merchant holds at most 20 definitions, active or inactive. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer's purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}
```

_Example: Optional department dropdown_

Defines an optional dropdown. A value sent on an invoice must match one of the options exactly, or the request answers 400 Invoicing:CustomField:InvalidValue. Replace billerId with your merchant's id.

```json
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}
```

## Responses

### 200

The definition was created and is returned.

**Content type:** `application/json`

Schema: [`InvoiceCustomFieldDefinitionDto`](https://devportal.demo.winkpg.io/docs/api/models/InvoiceCustomFieldDefinitionDto.md)

Properties:
- `id` (string(uuid))
- `creationTime` (string(date-time)): The date and time when this entity was created.
- `creatorId` (string(uuid)): The ID of the user who created this entity. (nullable)
- `lastModificationTime` (string(date-time)): The date and time when this entity was last modified. (nullable)
- `lastModifierId` (string(uuid)): The ID of the user who last modified this entity. (nullable)
- `billerId` (string(uuid))
- `billerType` ([InvoicePartyType](https://devportal.demo.winkpg.io/docs/api/models/InvoicePartyType.md)): Identifies the type of entity acting as the biller or recipient on an invoice.
  Values:
  - `GatewayOwner`: Platform-level gateway owner.
  - `Reseller`: Reseller entity.
  - `Merchant`: Merchant entity.
  - `Customer`: End customer.
- `key` (string): (nullable)
- `label` (string): (nullable)
- `description` (string): (nullable)
- `fieldType` ([CustomFieldType](https://devportal.demo.winkpg.io/docs/api/models/CustomFieldType.md)): The data type of a custom field definition.
  Values:
  - `Text`
  - `Dropdown`
  - `Checkbox`
  - `Date`
  - `Numeric`
- `isRequired` (boolean): (nullable)
- `isActive` (boolean): (nullable)
- `sortOrder` (integer(int32)): (nullable)
- `options` (array<string>): (nullable)
- `maxLength` (integer(int32)): (nullable)
- `regexPattern` (string): (nullable)
- `regexErrorMessage` (string): (nullable)
- `concurrencyStamp` (string): (nullable)

### 400

The request is not valid: the key is missing or too long, the biller is empty, or a field rule is malformed.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Request failed validation_

One or more fields were rejected before any rule ran. error.code is null on the envelope and the causes are in validationErrors, one entry per failure. An entry carries code when the validator declared a publishable one, and memberPaths when the full path says more than members does (an element inside a collection, for example). Both keys are omitted when they would add nothing.

```json
{
  "error": {
    "code": "null",
    "message": "Your request is not valid!",
    "details": "The following errors were detected during validation.",
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": [
      {
        "message": "'Amount' must be greater than 0.",
        "members": [
          "amount"
        ]
      },
      {
        "message": "The card has expired.",
        "members": [
          "expirationDate"
        ],
        "code": "CardData:CardExpired"
      },
      {
        "message": "'Value' must not be empty.",
        "members": [
          "value"
        ],
        "memberPaths": [
          "customFields[2].value"
        ]
      }
    ]
  }
}
```

### 409

The biller already holds the maximum number of custom field definitions
(`Invoicing:CustomFieldDefinition:LimitReached`), or a definition with this key,
compared case-insensitively, already exists for the biller
(`Invoicing:CustomFieldDefinition:KeyAlreadyExists`); for the latter the error's
`data.key` holds the stored spelling of the key it collided with.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 403

Forbidden

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 401

Unauthorized

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 404

Not Found

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Resource not found_

The id in the path names no record the caller can see. Most resources answer with a null error.code and a message naming the resource type and the id; a resource that publishes a not-found code in the catalog above carries it in error.code instead, so check for one before matching on the message.

```json
{
  "error": {
    "code": "null",
    "message": "There is no entity Transaction with id = 7d1f3a52-0c4e-4b8a-9e21-5a6b7c8d9e00!",
    "details": "null",
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": "null"
  }
}
```

### 501

Not Implemented

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 500

Internal Server Error

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### default

The request failed. The body carries the standard error envelope: a machine-readable `error.code`, a human-readable `error.message`, and `error.validationErrors` when the failure was a validation rejection. The [error reference](https://devportal.demo.winkpg.io/docs/errors.md) lists the values `error.code` can take.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Business rule refused the request_

The request was understood and rejected by a platform rule. This is the shape that carries a code from the catalog above, so branch on error.code rather than on the message text. The HTTP status is the one listed against the code.

```json
{
  "error": {
    "code": "Transactions:OperationNotAllowed",
    "message": "The operation 'Void' is not allowed on a Sale transaction with result 'Approved' and settlement state 'Settled'.",
    "details": "null",
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": "null"
  }
}
```

### 429

The request was refused because a rate limit was exceeded, or because something a later retry can clear stopped it. A rate limit refusal carries an `application/problem+json` body: wait at least the interval `Retry-After` names before retrying, then back off. Limits are tuned per deployment, so read the allowance from the response headers rather than assuming a fixed ceiling. Any other refusal carries the standard error envelope as `application/json`, and its `error.code` names the cause.

**Content type:** `application/problem+json`

Schema: [`RateLimitProblemDetails`](https://devportal.demo.winkpg.io/docs/api/models/RateLimitProblemDetails.md)

Properties:
- `type` (string) required: The problem type identifier. Always the same value: the failure is the status code itself,  so there is no sub-type for a caller to branch on. (nullable)
- `title` (string) required: A short, human-readable summary of the problem type. (nullable)
- `status` (integer(int32)) required: The HTTP status code, repeated in the body as the problem-details format defines.
- `detail` (string) required: A human-readable explanation of this occurrence of the problem. (nullable)
- `retryAfterSeconds` (integer(int32)) required: How long to wait before retrying, in whole seconds, carrying the same figure as the  `Retry-After` header. Always at least one: a value of zero would invite an immediate  retry that is certain to be rejected again.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.demo.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

## Example request

Every block below sends the same request. Replace {{BASE_URL}} with the address of the API you are calling and {{API_KEY}} with your own key.

The request body is a InvoiceCustomFieldDefinitionCreateDto. See the Request body section below for its fields.

These blocks send the Required purchase order number example. The other examples follow under Other request examples.

Defines a text field every new invoice from the merchant must carry: an invoice create with no value for it, or an update whose customFields leave it out, answers 400 Invoicing:CustomField:Required, and a value that is longer than 20 characters or does not match the pattern answers 400 Invoicing:CustomField:InvalidValue with the error message given here. The key is fixed once created and unique per merchant, compared without regard to case: a duplicate answers 409 Invoicing:CustomFieldDefinition:KeyAlreadyExists. A merchant holds at most 20 definitions, active or inactive. Replace billerId with your merchant's id.

### cURL

```bash
curl -X POST "{{BASE_URL}}/api/invoicing/custom-field-definitions" \
  -H "api-key: {{API_KEY}}" \
  -H "Content-Type: application/json" \
  -d '{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer\u0027s purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}'
```

### PowerShell

```powershell
$headers = @{
    'api-key' = '{{API_KEY}}'
}

$body = @'
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer\u0027s purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}
'@

$response = Invoke-RestMethod -Method POST -Uri '{{BASE_URL}}/api/invoicing/custom-field-definitions' `
    -Headers $headers -ContentType 'application/json' -Body $body
```

### TypeScript (SDK)

```bash
npm install @winkpg/winkpg-api
```

```typescript
import { Configuration, InvoicingApi } from '@winkpg/winkpg-api';

const api = new InvoicingApi(new Configuration({
  basePath: '{{BASE_URL}}',
  apiKey: '{{API_KEY}}',
}));

const { data } = await api.invoiceCustomFieldDefinitionCreate({
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer\u0027s purchase order number",
  "isRequired": true,
  "isActive": true,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
});
```

### TypeScript (raw HTTP)

```typescript
const response = await fetch('{{BASE_URL}}/api/invoicing/custom-field-definitions', {
  method: 'POST',
  headers: {
    "api-key": "{{API_KEY}}",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "billerId": "00000000-0000-0000-0000-000000000001",
    "billerType": "Merchant",
    "key": "po_number",
    "fieldType": "Text",
    "label": "PO number",
    "description": "The customer\u0027s purchase order number",
    "isRequired": true,
    "isActive": true,
    "maxLength": 20,
    "regexPattern": "^PO-[0-9]{5}$",
    "regexErrorMessage": "Enter a PO number such as PO-48213."
  }),
});

const data = await response.json();
```

### C# (SDK)

```bash
dotnet add package WinkPg.Api.Client
```

```csharp
using WinkPg.Api.Client.Api;
using WinkPg.Api.Client.Client;
using System.Text.Json;

var config = new Configuration { BasePath = "{{BASE_URL}}" };
config.AddApiKey("api-key", "{{API_KEY}}");

var api = new InvoicingApi(config);
var body = JsonSerializer.Deserialize<InvoiceCustomFieldDefinitionCreateDto>("""
    {
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "po_number",
      "fieldType": "Text",
      "label": "PO number",
      "description": "The customer\u0027s purchase order number",
      "isRequired": true,
      "isActive": true,
      "maxLength": 20,
      "regexPattern": "^PO-[0-9]{5}$",
      "regexErrorMessage": "Enter a PO number such as PO-48213."
    }
    """);

var result = await api.InvoiceCustomFieldDefinitionCreateAsync(body);
```

### C# (raw HTTP)

```csharp
using System.Text;

using var http = new HttpClient { BaseAddress = new Uri("{{BASE_URL}}") };

var request = new HttpRequestMessage(new HttpMethod("POST"), "/api/invoicing/custom-field-definitions");
request.Headers.Add("api-key", "{{API_KEY}}");

request.Content = new StringContent("""
    {
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "po_number",
      "fieldType": "Text",
      "label": "PO number",
      "description": "The customer\u0027s purchase order number",
      "isRequired": true,
      "isActive": true,
      "maxLength": 20,
      "regexPattern": "^PO-[0-9]{5}$",
      "regexErrorMessage": "Enter a PO number such as PO-48213."
    }
    """, Encoding.UTF8, "application/json");

var response = await http.SendAsync(request);
response.EnsureSuccessStatusCode();
var json = await response.Content.ReadAsStringAsync();
```

### Python (SDK)

```bash
pip install winkpg-api
```

```python
import winkpg_api

configuration = winkpg_api.Configuration(host="{{BASE_URL}}")
configuration.api_key["ApiKey"] = "{{API_KEY}}"

with winkpg_api.ApiClient(configuration) as client:
    api = winkpg_api.InvoicingApi(client)
    body = winkpg_api.InvoiceCustomFieldDefinitionCreateDto.from_dict({
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "po_number",
      "fieldType": "Text",
      "label": "PO number",
      "description": "The customer\u0027s purchase order number",
      "isRequired": True,
      "isActive": True,
      "maxLength": 20,
      "regexPattern": "^PO-[0-9]{5}$",
      "regexErrorMessage": "Enter a PO number such as PO-48213."
    })
    result = api.invoice_custom_field_definition_create(body)
```

### Python (raw HTTP)

```bash
pip install requests
```

```python
import requests

headers = {
    "api-key": "{{API_KEY}}",
    "Content-Type": "application/json",
}

body = {
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "po_number",
  "fieldType": "Text",
  "label": "PO number",
  "description": "The customer\u0027s purchase order number",
  "isRequired": True,
  "isActive": True,
  "maxLength": 20,
  "regexPattern": "^PO-[0-9]{5}$",
  "regexErrorMessage": "Enter a PO number such as PO-48213."
}

response = requests.request(
    "POST",
    "{{BASE_URL}}/api/invoicing/custom-field-definitions",
    headers=headers,
    json=body,
)
response.raise_for_status()
data = response.json()
```

## Other request examples

Each example below is one request, shown in every language with the same placeholders.

### Optional department dropdown

Defines an optional dropdown. A value sent on an invoice must match one of the options exactly, or the request answers 400 Invoicing:CustomField:InvalidValue. Replace billerId with your merchant's id.

#### cURL

```bash
curl -X POST "{{BASE_URL}}/api/invoicing/custom-field-definitions" \
  -H "api-key: {{API_KEY}}" \
  -H "Content-Type: application/json" \
  -d '{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}'
```

#### PowerShell

```powershell
$headers = @{
    'api-key' = '{{API_KEY}}'
}

$body = @'
{
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}
'@

$response = Invoke-RestMethod -Method POST -Uri '{{BASE_URL}}/api/invoicing/custom-field-definitions' `
    -Headers $headers -ContentType 'application/json' -Body $body
```

#### TypeScript (SDK)

```bash
npm install @winkpg/winkpg-api
```

```typescript
import { Configuration, InvoicingApi } from '@winkpg/winkpg-api';

const api = new InvoicingApi(new Configuration({
  basePath: '{{BASE_URL}}',
  apiKey: '{{API_KEY}}',
}));

const { data } = await api.invoiceCustomFieldDefinitionCreate({
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": true,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
});
```

#### TypeScript (raw HTTP)

```typescript
const response = await fetch('{{BASE_URL}}/api/invoicing/custom-field-definitions', {
  method: 'POST',
  headers: {
    "api-key": "{{API_KEY}}",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "billerId": "00000000-0000-0000-0000-000000000001",
    "billerType": "Merchant",
    "key": "department",
    "fieldType": "Dropdown",
    "label": "Department",
    "isActive": true,
    "sortOrder": 1,
    "options": [
      "Facilities",
      "Marketing",
      "Operations"
    ]
  }),
});

const data = await response.json();
```

#### C# (SDK)

```bash
dotnet add package WinkPg.Api.Client
```

```csharp
using WinkPg.Api.Client.Api;
using WinkPg.Api.Client.Client;
using System.Text.Json;

var config = new Configuration { BasePath = "{{BASE_URL}}" };
config.AddApiKey("api-key", "{{API_KEY}}");

var api = new InvoicingApi(config);
var body = JsonSerializer.Deserialize<InvoiceCustomFieldDefinitionCreateDto>("""
    {
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "department",
      "fieldType": "Dropdown",
      "label": "Department",
      "isActive": true,
      "sortOrder": 1,
      "options": [
        "Facilities",
        "Marketing",
        "Operations"
      ]
    }
    """);

var result = await api.InvoiceCustomFieldDefinitionCreateAsync(body);
```

#### C# (raw HTTP)

```csharp
using System.Text;

using var http = new HttpClient { BaseAddress = new Uri("{{BASE_URL}}") };

var request = new HttpRequestMessage(new HttpMethod("POST"), "/api/invoicing/custom-field-definitions");
request.Headers.Add("api-key", "{{API_KEY}}");

request.Content = new StringContent("""
    {
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "department",
      "fieldType": "Dropdown",
      "label": "Department",
      "isActive": true,
      "sortOrder": 1,
      "options": [
        "Facilities",
        "Marketing",
        "Operations"
      ]
    }
    """, Encoding.UTF8, "application/json");

var response = await http.SendAsync(request);
response.EnsureSuccessStatusCode();
var json = await response.Content.ReadAsStringAsync();
```

#### Python (SDK)

```bash
pip install winkpg-api
```

```python
import winkpg_api

configuration = winkpg_api.Configuration(host="{{BASE_URL}}")
configuration.api_key["ApiKey"] = "{{API_KEY}}"

with winkpg_api.ApiClient(configuration) as client:
    api = winkpg_api.InvoicingApi(client)
    body = winkpg_api.InvoiceCustomFieldDefinitionCreateDto.from_dict({
      "billerId": "00000000-0000-0000-0000-000000000001",
      "billerType": "Merchant",
      "key": "department",
      "fieldType": "Dropdown",
      "label": "Department",
      "isActive": True,
      "sortOrder": 1,
      "options": [
        "Facilities",
        "Marketing",
        "Operations"
      ]
    })
    result = api.invoice_custom_field_definition_create(body)
```

#### Python (raw HTTP)

```bash
pip install requests
```

```python
import requests

headers = {
    "api-key": "{{API_KEY}}",
    "Content-Type": "application/json",
}

body = {
  "billerId": "00000000-0000-0000-0000-000000000001",
  "billerType": "Merchant",
  "key": "department",
  "fieldType": "Dropdown",
  "label": "Department",
  "isActive": True,
  "sortOrder": 1,
  "options": [
    "Facilities",
    "Marketing",
    "Operations"
  ]
}

response = requests.request(
    "POST",
    "{{BASE_URL}}/api/invoicing/custom-field-definitions",
    headers=headers,
    json=body,
)
response.raise_for_status()
data = response.json()
```

## See also

- [All documentation](https://devportal.demo.winkpg.io/llms.txt): the machine-readable index of every public page on this site.