diff --git a/vendor/magento/module-customer-custom-attributes/Block/Checkout/LayoutProcessor.php b/vendor/magento/module-customer-custom-attributes/Block/Checkout/LayoutProcessor.php
index f952e2d..31d28cf 100644
--- a/vendor/magento/module-customer-custom-attributes/Block/Checkout/LayoutProcessor.php
+++ b/vendor/magento/module-customer-custom-attributes/Block/Checkout/LayoutProcessor.php
@@ -79,6 +79,7 @@ class LayoutProcessor implements \Magento\Checkout\Block\Checkout\LayoutProcesso

         $jsLayout = $this->processCustomAttributesForPaymentMethods($jsLayout, $addressCustomAttributes);
         $jsLayout = $this->mergeCustomAttributes($jsLayout, $addressCustomAttributes);
+        $jsLayout = $this->mergeCustomAttributesOfBillingAddress($jsLayout, $addressCustomAttributes);

         return $jsLayout;
     }
@@ -165,4 +166,34 @@ class LayoutProcessor implements \Magento\Checkout\Block\Checkout\LayoutProcesso

         return $jsLayout;
     }
+
+    /**
+     * Merge custom attributes of billing address.
+     *
+     * @param array $jsLayout
+     * @param array $addressCustomAttributes
+     * @return array
+     */
+    private function mergeCustomAttributesOfBillingAddress(
+        array $jsLayout,
+        array $addressCustomAttributes
+    ): array {
+        if (isset($jsLayout['components']['checkout']['children']['steps']['children']['billing-step']
+            ['children']['payment']['children']['afterMethods']['children']['billing-address-form']
+            ['children']['form-fields'])) {
+            $fields = $jsLayout['components']['checkout']['children']['steps']['children']['billing-step']
+            ['children']['payment']['children']['afterMethods']['children']['billing-address-form']
+            ['children']['form-fields']['children'];
+            $jsLayout['components']['checkout']['children']['steps']['children']['billing-step']
+            ['children']['payment']['children']['afterMethods']['children']['billing-address-form']
+            ['children']['form-fields']['children'] = $this->merger->merge(
+                $addressCustomAttributes,
+                'checkoutProvider',
+                'billingAddressshared.custom_attributes',
+                $fields
+            );
+        }
+
+        return $jsLayout;
+    }
 }
--
2.20.1