### [wpforms_process_validate_payment-checkbox](https://wpforms.com/developers/wpforms_process_validate_payment-checkbox/)

**Published:** September 29, 2026
**Author:** Umair Majeed

**Content:**

## Description

The `wpforms_process_validate_payment-checkbox` action fires for each **Checkbox Items** payment field while WPForms validates a submitted form, before any field value is formatted and before the entry is saved.

This action is available since WPForms 1.4.0.

parametertypedescription`$field_id`string|intField ID as a numeric string.`$field_submit`mixedSubmitted field value (raw data). For this field it is the array of checked choice IDs from the request, or an empty string when nothing was posted for the field.`$form_data`arrayForm data and settings.## More Information

`WPForms_Process::process()` loops over every field in `$form_data['fields']` and calls `do_action( "wpforms_process_validate_{$field_type}", $field_id, $field_submit, $this->form_data )` for each one. This hook is the instance for the `payment-checkbox` field type. It fires on every submission of a form that contains the field, whether or not the visitor filled it in. The file lives in `includes/`, so it fires in Lite and Pro.

This hook is an instance of `do_action( "wpforms_process_validate_{$field_type}", $field_id, $field_submit, $form_data )`. Other instances are `wpforms_process_validate_payment-single` for the **Single Item** field and `wpforms_process_validate_checkbox` for the standard **Checkboxes** field.

The field class registers its own `validate()` method on this hook at priority 10 with three arguments. That callback adds the required-field error, rejects choice IDs that do not exist in the field settings, and enforces the field’s choice limit. A callback added later at the same priority runs after it and overwrites the same error slot.

To reject the submission, write a message to `wpforms()->obj( 'process' )->errors[ $form_data['id'] ][ $field_id ]`. After the loop, the `wpforms_process_initial_errors` filter runs on the collected errors; Conditional Logic uses it to drop errors from hidden fields. Values are not sanitized at this point. Sanitizing happens later in `wpforms_process_format_{$field_type}`.

## Source

`wpforms/includes/class-process.php`

## Example

Require between two and five checked items in one Checkbox Items field on one form, and stop the submission with an error under the field when the count is outside that range.

```

/**
 * Require between two and five checked items in a Checkbox Items field.
 *
 * @link https://wpforms.com/developers/wpforms_process_validate_payment-checkbox/
 *
 * @param string|int $field_id     Field ID.
 * @param mixed      $field_submit Submitted field value (raw data).
 * @param array      $form_data    Form data and settings.
 */
function wpf_dev_process_validate_payment_checkbox( $field_id, $field_submit, $form_data ) {

    // Only run on my form with ID = 143, remember to change this to match your form ID.
    if ( absint( $form_data['id'] ) !== 143 ) {
        return;
    }

    // Only run on the Checkbox Items field with ID = 21, remember to change this to match your field ID.
    if ( absint( $field_id ) !== 21 ) {
        return;
    }

    $min   = 2;
    $max   = 5;
    $count = is_array( $field_submit ) ? count( $field_submit ) : 0;

    if ( $count < $min ) {
        wpforms()->obj( 'process' )->errors[ $form_data['id'] ][ $field_id ] = sprintf(
            /* translators: %d - minimum number of choices. */
            esc_html__( 'Please select a minimum of %d choices.', 'wpforms' ),
            $min
        );

        return;
    }

    if ( $count > $max ) {
        wpforms()->obj( 'process' )->errors[ $form_data['id'] ][ $field_id ] = sprintf(
            /* translators: %d - maximum number of choices. */
            esc_html__( 'Please select a maximum of %d choices.', 'wpforms' ),
            $max
        );
    }
}
add_action( 'wpforms_process_validate_payment-checkbox', 'wpf_dev_process_validate_payment_checkbox', 10, 3 );
```

## Reference Article

- [Setting a Minimum Number of Choices for a Checkbox](https://wpforms.com/developers/how-to-set-a-minimum-number-of-choices-for-a-checkbox/)

**Categories:** Actions Hooks

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