---
title: "EU/UK VAT Manager: Developer Hooks and Filters Reference"
description: "Developer reference for EU/UK VAT Manager for WooCommerce: field, validation, exemption and gateway filters."
url: "https://wpfactory.com/docs/eu-vat-developer-hooks-filters/"
updated: "2026-09-27"
category: Developers
---

# EU/UK VAT Manager: Developer Hooks and Filters Reference

The [EU/UK VAT Manager for WooCommerce](https://wpfactory.com/item/eu-vat-for-woocommerce/) exposes filters and one action so you can adjust the VAT field, the validation flow and the exemption logic in code without editing plugin files. All hooks use the `alg_wc_eu_vat_` prefix. The VAT number is stored in the order and user meta key `_billing_eu_vat_number`.

### Field filters

| Filter | Filtered value | Arguments |
| --- | --- | --- |
| `alg_wc_eu_vat_get_field_id` | The field id base (default `eu_vat_number`, prefixed to `billing_eu_vat_number`) | `$field_id` |
| `alg_wc_eu_vat_get_field_data` | The full checkout field definition array (label, placeholder, required, class, priority) | `$field_data` |
| `alg_wc_eu_vat_confirmation_bg_yes` / `alg_wc_eu_vat_confirmation_bg_no` | The Yes/No button colors for the empty-VAT confirmation notice (`green` / `red`) | `$color` |

#### Change the stored field id

```
add_filter( 'alg_wc_eu_vat_get_field_id', function ( $field_id ) {
    return 'vat_id'; // stored meta becomes _billing_vat_id
} );
```

### Validation filters

| Filter | Filtered value | Arguments |
| --- | --- | --- |
| `alg_wc_eu_vat_validation_response` | The raw response from the validation service (use it to route validation through another API) | `$response, $method, $country_code, $vat_number` |
| `alg_wc_eu_vat_check_alternative` | The validation result after the primary and fallback checks | `$result, $country_code, $vat_number, $billing_company` |
| `alg_wc_eu_vat_validation_methods` | The ordered list of methods to try (`soap`, `curl`, `file_get_contents`) | `$methods` |
| `alg_wc_eu_vat_is_valid_vat_at_checkout` | Whether the VAT number is treated as valid at checkout | `$is_vat_valid` |
| `alg_wc_eu_vat_vatsense_key` | The VATSense API key used for UK and non-EU validation | `$key` |

### Exemption and gateway filters

| Filter | Filtered value | Arguments |
| --- | --- | --- |
| `alg_wc_eu_vat_maybe_exclude_vat` | Whether VAT is excluded (admin-side calculation) | `$is_exempt` |
| `alg_wc_eu_vat_maybe_exclude_vat_on_available_gateway` | Whether VAT is excluded when filtering available payment gateways | `$is_exempt` |

### Pro-gated feature filters

These filters resolve the Pro-only features. In the free version each returns its default (so the feature is off); in Pro the option value is returned.

- `alg_wc_eu_vat_check_ip_location_country` - whether the check-country-by-IP feature is active.
- `alg_wc_eu_vat_check_company_name` - whether the company-name check is active.
- `alg_wc_eu_vat_show_in_countries` - the country list the field is limited to.
- `alg_wc_eu_vat_show_for_user_roles` - the user roles the field is limited to.
- `alg_wc_eu_vat_settings` - the Pro gate itself: it returns an empty string in Pro and `array( 'disabled' => 'disabled' )` in the free version, which is how Pro-only fields are disabled in the admin.

### Context filters

- `alg_wc_eu_vat_is_checkout` and `alg_wc_eu_vat_is_cart` - override the plugin's cart/checkout detection.
- `alg_wc_eu_vat_get_settings` - filter the full settings array (`$settings, $current_section, $id, $obj`).
- `alg_wc_eu_vat_advertise` - the in-admin advertisement text.

### Action

| Action | Fires when | Arguments |
| --- | --- | --- |
| `alg_wc_eu_vat_exempt_applied` | After the plugin decides whether to exempt VAT for the current customer | `$is_vat_exempt` |

```
add_action( 'alg_wc_eu_vat_exempt_applied', function ( $is_vat_exempt ) {
    if ( $is_vat_exempt ) {
        // e.g. tag the session, add an order note, log the exemption
    }
} );
```

### Helper functions

Two functions are handy when reading the VAT number in your own code:

- `wpfactory_wc_eu_vat_get_field_id()` - returns `billing_eu_vat_number` (pass `true` for the short form `eu_vat_number`).
- `wpfactory_wc_eu_vat_validate_vat( $country_code, $vat_number, $billing_company )` - validates a number and returns `true`, `false`, or `null` when the service could not be reached.

### Shortcode

The plugin registers one shortcode, `[alg_wc_eu_vat_translate]`, for per-language text. See the [Shortcodes guide](https://wpfactory.com/docs/eu-vat-for-woocommerce/).

### Need help?

If you are extending [EU/UK VAT Manager for WooCommerce](https://wpfactory.com/item/eu-vat-for-woocommerce/) and a hook does not behave as expected, contact the team on the [support forum](https://wpfactory.com/support/item/eu-vat-for-woocommerce/) with the filter name and a short code sample.

Related articles

- [EU/UK VAT Manager: Advanced Settings Reference](https://wpfactory.com/docs/eu-vat-advanced-settings-reference/)
- [EU/UK VAT Manager: Reset a Settings Section to Defaults](https://wpfactory.com/docs/eu-vat-reset-a-settings-section/)
- [EU/UK VAT Manager: Shortcodes Guide](https://wpfactory.com/docs/shortcodes-guide-eu-vat/)
- [EU/UK VAT Manager: Free vs Pro Versions Compared](https://wpfactory.com/docs/pro-vs-free-versions-eu-vat/)
- [Installing EU/UK VAT Manager for WooCommerce](https://wpfactory.com/docs/install-eu-vat/)