diff --git a/docs/user-guide/domain-seller/header-search.md b/docs/user-guide/domain-seller/header-search.md
new file mode 100644
index 00000000..1bf90f58
--- /dev/null
+++ b/docs/user-guide/domain-seller/header-search.md
@@ -0,0 +1,78 @@
+---
+title: "Header Domain Search"
+sidebar_position: 4
+---
+
+# Header Domain Search
+
+Use this setup when you want a small header form that starts a domain search, then lets the customer choose from available domains inside the Ultimate Multisite checkout.
+
+## Requirements
+
+- Ultimate Multisite network-active.
+- Multisite Ultimate Domain Seller network-active.
+- At least one active domain registration product with:
+  - `domain_provider` set to a configured provider.
+  - Supported TLDs configured, for example `com`, `net`, and `org`.
+- A valid checkout form containing the **Domain Selection** field.
+
+## Checkout form
+
+1. Create or edit the checkout form used by the registration page.
+2. Add the normal required checkout/account fields, including **Username**. A checkout form containing only the domain field is rejected by Ultimate Multisite validation.
+3. Add a **Domain Selection** field.
+4. Set the Domain Selection mode to **Register Only** when the flow should focus on registered domains rather than free subdomains or existing domains.
+5. Assign the domain registration product to that field.
+
+The registration page should render the checkout form, for example:
+
+```text
+[wu_checkout slug="domain-form"]
+```
+
+## Header form
+
+Add a small `GET` form in the site header that sends the entered search term to the checkout page as `domain_name`:
+
+```html
+<form class="ums-header-domain-search" action="/register/" method="get">
+  <label class="screen-reader-text" for="ums-header-domain-search-input">Search for a domain</label>
+  <input id="ums-header-domain-search-input" name="domain_name" type="text" placeholder="Find your domain" autocomplete="off">
+  <button type="submit">Search</button>
+</form>
+```
+
+Do not preselect a domain in custom header JavaScript. The header should only pass the search term. The Domain Seller checkout script reads `?domain_name=example`, fills the checkout search box, and runs the availability search so the customer can choose from the returned domains.
+
+## Expected behaviour
+
+Searching `example` in the header should open:
+
+```text
+/register/?domain_name=example
+```
+
+The checkout should then display selectable results such as:
+
+- `example.com`
+- `example.net`
+- `example.org` unavailable
+- other provider-supported TLDs
+
+After selecting an available result, the order summary should include the domain registration product and the selected domain name.
+
+## Verification
+
+1. Open the home page.
+2. Search for a bare name, for example `example`.
+3. Confirm the checkout URL includes `?domain_name=example`.
+4. Confirm the checkout domain field contains `example`.
+5. Confirm a list of domain choices appears.
+6. Click **Select** for an available domain.
+7. Confirm the order summary contains `Domain Registration - example.com` or the selected domain.
+
+## Troubleshooting
+
+- If no list appears, check the browser network tab for `admin-ajax.php?action=wu_domain_search` and confirm it returns non-empty `domains` or `results`.
+- If the checkout form fails validation while saving, add the required account fields such as **Username**.
+- If selecting a domain does not update the cart, confirm `window.wu_checkout_form` exists and that the Domain Seller checkout assets are loaded on the checkout page.
diff --git a/sidebars.js b/sidebars.js
index cf760408..cf0888ae 100644
--- a/sidebars.js
+++ b/sidebars.js
@@ -75,6 +75,7 @@ const sidebars = {
         'user-guide/domain-seller/setup',
         'user-guide/domain-seller/domain-products',
         'user-guide/domain-seller/checkout-and-dns',
+        'user-guide/domain-seller/header-search',
       ],
     },
      {