Add missing "VAT Number" field to customer registration page

app/code/Magento/Customer/Test/Mftf/Section/StorefrontCustomerDashboardAccountInformationSection/StorefrontCustomerAddressSection.xml

@@ -19,6 +19,7 @@
         <element name="stateProvinceFill" type="input" selector="#region"/>
         <element name="zip" type="input" selector="#zip"/>
         <element name="country" type="select" selector="#country"/>
+        <element name="vatId" type="input" selector="#vat_id"/>
         <element name="saveAddress" type="button" selector="[data-action='save-address']" timeout="30"/>
     </section>
 </sections>

app/code/Magento/Customer/view/frontend/templates/form/register.phtml

@@ -131,6 +131,23 @@ $formData = $block->getFormData();
                 </div>
             </div>
 
+            <?php if ($addressHelper->isVatAttributeVisible()): ?>
+                <?php $_vatidValidationClass = $addressHelper->getAttributeValidationClass('vat_id'); ?>
+                <div class="field taxvat">
+                    <label class="label" for="vat_id">
+                        <span><?= /* @noEscape */ $block->getAttributeData()->getFrontendLabel('vat_id') ?></span>
+                    </label>
+                    <div class="control">
+                        <input type="text"
+                               name="vat_id"
+                               value="<?= $escaper->escapeHtmlAttr($formData->getVatId()) ?>"
+                               title="<?= /* @noEscape */ $block->getAttributeData()->getFrontendLabel('vat_id') ?>"
+                               class="input-text <?= $escaper->escapeHtmlAttr($_vatidValidationClass) ?>"
+                               id="vat_id">
+                    </div>
+                </div>
+            <?php endif; ?>
+
             <div class="field country required">
                 <label for="country" class="label">
                     <span><?= /* @noEscape */ $block->getAttributeData()->getFrontendLabel('country_id') ?></span>

app/code/Magento/Multishipping/Test/Mftf/Test/StoreFrontCheckVatIdAtAccountCreateWithMultishipmentTest.xml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ /**
+  * Copyright © Magento, Inc. All rights reserved.
+  * See COPYING.txt for license details.
+  */
+-->
+
+<tests xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:noNamespaceSchemaLocation="urn:magento:mftf:Test/etc/testSchema.xsd">
+    <test name="StoreFrontCheckVatIdAtAccountCreateWithMultishipmentTest">
+        <annotations>
+            <features value="Multishipment"/>
+            <stories value="Checking vat id field at account create page  with 'Check Out with Multiple Addresses'"/>
+            <title value="Checking vat id field at account create page  with 'Check Out with Multiple Addresses'"/>
+            <description value="'VAT Number' field should be available at create account page  if 'Show VAT Number on Storefront' is Yes"/>
+            <severity value="MAJOR"/>
+            <testCaseId value="MC-40397"/>
+            <group value="Multishipment"/>
+        </annotations>
+        <before>
+            <magentoCLI command="config:set customer/create_account/vat_frontend_visibility 1" stepKey="showVatNumberOnStorefrontYes"/>
+            <createData entity="SimpleSubCategory" stepKey="category"/>
+            <createData entity="SimpleProduct" stepKey="product">
+                <requiredEntity createDataKey="category"/>
+            </createData>
+        </before>
+        <after>
+            <magentoCLI command="config:set customer/create_account/vat_frontend_visibility 0" stepKey="showVatNumberOnStorefrontNo"/>
+            <actionGroup ref="CliCacheFlushActionGroup" stepKey="flushCacheAfter">
+                <argument name="tags" value="config"/>
+            </actionGroup>
+            <deleteData createDataKey="category" stepKey="deleteCategory"/>
+            <deleteData createDataKey="product" stepKey="deleteproduct"/>
+        </after>
+        <!-- Add product to the cart -->
+        <amOnPage url="$$product.name$$.html" stepKey="goToProductPage"/>
+        <actionGroup ref="AddToCartFromStorefrontProductPageActionGroup" stepKey="addProductToCart">
+            <argument name="productName" value="$$product.name$$"/>
+        </actionGroup>
+        <!-- Check Out with Multiple Addresses -->
+        <actionGroup ref="StorefrontOpenCartFromMinicartActionGroup" stepKey="openCart"/>
+        <waitForElementVisible selector="{{MultishippingSection.shippingMultipleCheckout}}" stepKey="waitMultipleAddressShippingButton"/>
+        <click selector="{{MultishippingSection.shippingMultipleCheckout}}" stepKey="clickToMultipleAddressShippingButton"/>
+        <!--Create an account-->
+        <waitForElementVisible selector="{{StorefrontCustomerSignInPopupFormSection.createAnAccount}}" stepKey="waitCreateAnAccountButton"/>
+        <click selector="{{StorefrontCustomerSignInPopupFormSection.createAnAccount}}" stepKey="clickOnCreateAnAccountButton"/>
+        <waitForPageLoad stepKey="waitForCreateAccountPageToLoad"/>
+        <!--Check the VAT Number field-->
+        <seeElement selector="{{StorefrontCustomerAddressSection.vatId}}" stepKey="assertVatIdField"/>
+    </test>
+</tests>