How To Add Custom Field At Billing Address Form In Magento 2

How To Add Custom Field At Billing Address Form In Magento 2 : In this post, i’ll explain how we can add custom fields in billing address form at checkout. so just follow these steps.

Step1 => Please check in the Sales Checkout configuration Display billing address (Admin->Stores -> Configuration -> Sales -> Checkout->Checkout Options) Option must be Payment method

Step 2 => As we know that billing and shipping forms are generated dynamically. So we need to create a plugin for the \Magento\Checkout\Block\Checkout\LayoutProcessor::process method.
So for creating the plugin first we should make an entry in di.xml on this path.
app/code/CompanyName/Module/etc/frontend/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Checkout\Block\Checkout\LayoutProcessor">
        <plugin name="add_custom_field_checkout_form" type="CompanyName\Module\Model\Plugin\Checkout\LayoutProcessor" sortOrder="100"/>
    </type>
</config>

2 => Create the plugin class on this Directory.
app/code/CompanyName\Module\Model\Plugin\Checkout

namespace Webkul\CompanyName\Module\Plugin\Checkout;
class LayoutProcessor
{
    /**
     * @param \Magento\Checkout\Block\Checkout\LayoutProcessor $subject
     * @param array $jsLayout
     * @return array
     */
    public function afterProcess(
        \Magento\Checkout\Block\Checkout\LayoutProcessor $subject,
        array  $jsLayout
    ) {
        $configuration = $jsLayout['components']['checkout']['children']['steps']['children']['billing-step']['children']['payment']['children']['payments-list']['children'];
        foreach ($configuration as $paymentGroup => $groupConfig) {
            if (isset($groupConfig['component']) AND $groupConfig['component'] === 'Magento_Checkout/js/view/billing-address') {

                $jsLayout['components']['checkout']['children']['steps']['children']['billing-step']['children']
                ['payment']['children']['payments-list']['children'][$paymentGroup]['children']['form-fields']['children']['company_tax_id'] = [
                    'component' => 'Magento_Ui/js/form/element/abstract',
                    'config' => [
                        'customScope' => 'billingAddress.custom_attributes',
                        'template' => 'ui/form/field',
                        'elementTmpl' => 'ui/form/element/input',
                        'options' => [],
                        'id' => 'custom-field'
                    ],
                    'dataScope' => 'billingAddress.custom_attributes.custom_field',
                    'label' => 'Custom Field',
                    'provider' => 'checkoutProvider',
                    'visible' => true,
                    'validation' => [],
                    'sortOrder' => 250,
                    'id' => 'custom-field'
                ];
            }
        }


        return $jsLayout;
    }
}

Now custom field will be visible at billing form.

Hope so it will you help you.