diff --git a/frontend/src/__tests__/app/signin/route.test.ts b/frontend/src/__tests__/app/signin/route.test.ts
index 7e640189..b1b9bc65 100644
--- a/frontend/src/__tests__/app/signin/route.test.ts
+++ b/frontend/src/__tests__/app/signin/route.test.ts
@@ -31,7 +31,9 @@ test('returns redirect', async () => {
     secure: true,
   });
   expect(response.status).toEqual(307);
-  expect(response.headers.get('Location')).toEqual('/redirect-url');
+  expect(response.headers.get('Location')).toEqual(
+    'http://localhost:3000/redirect-url'
+  );
 });
 
 test('returns redirect - sanitizes redirect path', async () => {
@@ -43,7 +45,9 @@ test('returns redirect - sanitizes redirect path', async () => {
   const response = await GET(request);
 
   expect(response.status).toEqual(307);
-  expect(response.headers.get('Location')).toEqual('/redirect-url');
+  expect(response.headers.get('Location')).toEqual(
+    'http://localhost:3000/redirect-url'
+  );
 });
 
 test('returns redirect to /templates/message-templates if no redirect given', async () => {
@@ -56,7 +60,7 @@ test('returns redirect to /templates/message-templates if no redirect given', as
 
   expect(response.status).toEqual(307);
   expect(response.headers.get('Location')).toEqual(
-    '/templates/message-templates'
+    'http://localhost:3000/templates/message-templates'
   );
 });
 
@@ -71,7 +75,7 @@ test('returns redirect to /auth if no session detected', async () => {
   expect(cookiesMock.delete).toHaveBeenCalledWith('csrf_token');
 
   expect(response.status).toEqual(307);
-  expect(response.headers.get('Location')).toEqual('/auth');
+  expect(response.headers.get('Location')).toEqual('https://test/auth');
 });
 
 test('retains redirect search param on /auth redirect', async () => {
@@ -86,6 +90,6 @@ test('retains redirect search param on /auth redirect', async () => {
 
   expect(response.status).toEqual(307);
   expect(response.headers.get('Location')).toEqual(
-    '/auth?redirect=%2Fredirect-path'
+    'https://test/auth?redirect=%2Fredirect-path'
   );
 });
diff --git a/frontend/src/__tests__/components/__snapshots__/Header.test.tsx.snap b/frontend/src/__tests__/components/__snapshots__/Header.test.tsx.snap
index 314b995c..6690fdd8 100644
--- a/frontend/src/__tests__/components/__snapshots__/Header.test.tsx.snap
+++ b/frontend/src/__tests__/components/__snapshots__/Header.test.tsx.snap
@@ -18,7 +18,7 @@ exports[`Header component renders component correctly 1`] = `
           aria-label="NHS Notify templates"
           class="nhsuk-header__service-logo"
           data-testid="header-logo-service-link"
-          href="/templates/create-and-submit-templates"
+          href="http://localhost:3000/templates/create-and-submit-templates"
         >
           <svg
             class="nhsuk-header__logo"
diff --git a/frontend/src/__tests__/utils/get-templates-url.test.ts b/frontend/src/__tests__/utils/get-templates-url.test.ts
new file mode 100644
index 00000000..c317c854
--- /dev/null
+++ b/frontend/src/__tests__/utils/get-templates-url.test.ts
@@ -0,0 +1,78 @@
+import { getTemplatesUrl } from '@/utils/get-templates-url';
+
+describe('getTemplatesUrl', () => {
+  const originalEnv = process.env;
+
+  beforeEach(() => {
+    jest.resetModules();
+    process.env = { ...originalEnv };
+  });
+
+  afterAll(() => {
+    process.env = originalEnv;
+  });
+
+  describe('in production', () => {
+    beforeEach(() => {
+      Object.defineProperty(process.env, 'NODE_ENV', {
+        value: 'production',
+        configurable: true,
+      });
+      process.env.NOTIFY_DOMAIN_NAME = 'nhsnotify.nhs.uk';
+    });
+
+    it('should use https protocol', () => {
+      const result = getTemplatesUrl('/templates/message-templates');
+      expect(result).toBe(
+        'https://nhsnotify.nhs.uk/templates/message-templates'
+      );
+    });
+
+    it('should generate absolute URLs for templates app', () => {
+      const result = getTemplatesUrl('/templates/create-email-template');
+      expect(result).toBe(
+        'https://nhsnotify.nhs.uk/templates/create-email-template'
+      );
+    });
+
+    it('should handle query parameters', () => {
+      const result = getTemplatesUrl('/templates/message-templates?tab=drafts');
+      expect(result).toBe(
+        'https://nhsnotify.nhs.uk/templates/message-templates?tab=drafts'
+      );
+    });
+
+    it('should fallback to localhost when NOTIFY_DOMAIN_NAME is not set', () => {
+      delete process.env.NOTIFY_DOMAIN_NAME;
+      const result = getTemplatesUrl('/templates/message-templates');
+      expect(result).toBe('https://localhost:3000/templates/message-templates');
+    });
+  });
+
+  describe('in development', () => {
+    beforeEach(() => {
+      Object.defineProperty(process.env, 'NODE_ENV', {
+        value: 'development',
+        configurable: true,
+      });
+    });
+
+    it('should use http protocol', () => {
+      const result = getTemplatesUrl('/templates/message-templates');
+      expect(result).toBe('http://localhost:3000/templates/message-templates');
+    });
+
+    it('should handle query parameters', () => {
+      const result = getTemplatesUrl('/templates/message-templates?tab=drafts');
+      expect(result).toBe(
+        'http://localhost:3000/templates/message-templates?tab=drafts'
+      );
+    });
+
+    it('should fallback to localhost when NOTIFY_DOMAIN_NAME is not set', () => {
+      delete process.env.NOTIFY_DOMAIN_NAME;
+      const result = getTemplatesUrl('/templates/message-templates');
+      expect(result).toBe('http://localhost:3000/templates/message-templates');
+    });
+  });
+});
diff --git a/frontend/src/app/signin/route.ts b/frontend/src/app/signin/route.ts
index 7ae2474d..4bf6f9aa 100644
--- a/frontend/src/app/signin/route.ts
+++ b/frontend/src/app/signin/route.ts
@@ -5,6 +5,7 @@ import { cookies } from 'next/headers';
 import { NextRequest, NextResponse } from 'next/server';
 import { getSessionId } from '@/utils/amplify-utils';
 import { generateSessionCsrfToken } from '@/utils/csrf-utils';
+import { getTemplatesUrl } from '@/utils/get-templates-url';
 
 export const GET = async (request: NextRequest) => {
   const sessionId = await getSessionId();
@@ -23,21 +24,21 @@ export const GET = async (request: NextRequest) => {
       sameSite: 'strict',
       secure: true,
     });
+
+    redirectPath = getTemplatesUrl(redirectPath);
   } else {
     cookieStore.delete('csrf_token');
-    redirectPath = '/auth';
+
+    const authUrl = new URL('/auth', request.url);
 
     const redirectParam = request.nextUrl.searchParams.get('redirect');
 
     if (redirectParam) {
-      redirectPath += `?redirect=${encodeURIComponent(redirectParam)}`;
+      authUrl.searchParams.set('redirect', redirectParam);
     }
+
+    redirectPath = authUrl.toString();
   }
 
-  return NextResponse.json(null, {
-    status: 307,
-    headers: {
-      Location: redirectPath,
-    },
-  });
+  return NextResponse.redirect(redirectPath, { status: 307 });
 };
diff --git a/frontend/src/content/content.ts b/frontend/src/content/content.ts
index 93300f51..46cce25a 100644
--- a/frontend/src/content/content.ts
+++ b/frontend/src/content/content.ts
@@ -1,5 +1,6 @@
 import { formatTime } from '@/utils/format-time';
 import { getConstants } from '@/utils/public-constants';
+import { getTemplatesUrl } from '@/utils/get-templates-url';
 
 const { BASE_PATH, TIME_TILL_LOGOUT_SECONDS } = getConstants();
 
@@ -15,7 +16,7 @@ const header = {
   logoLink: {
     ariaLabel: 'NHS Notify templates',
     logoTitle: 'NHS logo',
-    href: '/templates/create-and-submit-templates',
+    href: getTemplatesUrl('/templates/create-and-submit-templates'),
   },
   accountInfo: {
     ariaLabel: 'Account',
diff --git a/frontend/src/utils/get-templates-url.ts b/frontend/src/utils/get-templates-url.ts
new file mode 100644
index 00000000..addab54a
--- /dev/null
+++ b/frontend/src/utils/get-templates-url.ts
@@ -0,0 +1,6 @@
+export function getTemplatesUrl(path: string): string {
+  const domain = process.env.NOTIFY_DOMAIN_NAME ?? 'localhost:3000';
+  const protocol = process.env.NODE_ENV === 'production' ? 'https:' : 'http:';
+
+  return `${protocol}//${domain}${path}`;
+}
diff --git a/infrastructure/terraform/components/app/amplify_app.tf b/infrastructure/terraform/components/app/amplify_app.tf
index 5725e216..de24f84a 100644
--- a/infrastructure/terraform/components/app/amplify_app.tf
+++ b/infrastructure/terraform/components/app/amplify_app.tf
@@ -29,6 +29,7 @@ resource "aws_amplify_app" "main" {
   environment_variables = {
     AMPLIFY_MONOREPO_APP_ROOT            = "frontend"
     HOSTED_LOGIN_DOMAIN                  = local.auth_domain_name
+    NOTIFY_DOMAIN_NAME                   = local.root_domain_name
     NOTIFY_GROUP                         = var.group
     NOTIFY_ENVIRONMENT                   = var.environment
     NEXT_PUBLIC_ENABLE_COGNITO_IDP       = var.enable_cognito_built_in_idp