diff --git a/app/main/forms.py b/app/main/forms.py
index 2363b7e28..f9e1e47c3 100644
--- a/app/main/forms.py
+++ b/app/main/forms.py
@@ -176,6 +176,13 @@ class RegisterUserForm(Form):
 
 
 class RegisterUserFromInviteForm(Form):
+    def __init__(self, invited_user):
+        super().__init__(
+            service=invited_user['service'],
+            email_address=invited_user['email_address'],
+            auth_type=invited_user['auth_type'],
+        )
+
     name = StringField(
         'Full name',
         validators=[DataRequired(message='Can’t be empty')]
diff --git a/app/main/views/register.py b/app/main/views/register.py
index f94895695..0bdcf3ca4 100644
--- a/app/main/views/register.py
+++ b/app/main/views/register.py
@@ -46,24 +46,23 @@ def register_from_invite():
     if not invited_user:
         abort(404)
 
-    form = RegisterUserFromInviteForm()
+    is_sms_auth = invited_user['auth_type'] == 'sms_auth'
+
+    form = RegisterUserFromInviteForm(invited_user)
 
     if form.validate_on_submit():
         if form.service.data != invited_user['service'] or form.email_address.data != invited_user['email_address']:
             abort(400)
-        _do_registration(form, send_email=False, send_sms=invited_user['auth_type'] == 'sms_auth')
+        _do_registration(form, send_email=False, send_sms=is_sms_auth)
         invite_api_client.accept_invite(invited_user['service'], invited_user['id'])
-        if invited_user['auth_type'] == 'sms_auth':
+        if is_sms_auth:
             return redirect(url_for('main.verify'))
         else:
             # we've already proven this user has email because they clicked the invite link,
             # so just activate them straight away
             return activate_user(session['user_details']['id'])
 
-    form.service.data = invited_user['service']
-    form.email_address.data = invited_user['email_address']
-
-    return render_template('views/register-from-invite.html', email_address=invited_user['email_address'], form=form)
+    return render_template('views/register-from-invite.html', invited_user=invited_user, form=form)
 
 
 def _do_registration(form, send_sms=True, send_email=True):
diff --git a/app/templates/views/register-from-invite.html b/app/templates/views/register-from-invite.html
index 29f9572b8..4051b8086 100644
--- a/app/templates/views/register-from-invite.html
+++ b/app/templates/views/register-from-invite.html
@@ -11,16 +11,19 @@ Create an account
 <div class="grid-row">
   <div class="column-two-thirds">
     <h1 class="heading-large">Create an account</h1>
-    <p>Your account will be created with this email: {{email_address}}</p>
+    <p>Your account will be created with this email: {{invited_user.email_address}}</p>
     <form method="post" autocomplete="off">
       {{ textbox(form.name, width='3-4') }}
-      <div class="extra-tracking">
-        {{ textbox(form.mobile_number, width='3-4', hint='We’ll send you a security code by text message') }}
-      </div>
+      {% if invited_user.auth_type == 'sms_auth' %}
+        <div class="extra-tracking">
+          {{ textbox(form.mobile_number, width='3-4', hint='We’ll send you a security code by text message') }}
+        </div>
+      {% endif %}
       {{ textbox(form.password, hint="At least 8 characters", width='3-4') }}
       {{ page_footer("Continue") }}
       {{form.service}}
       {{form.email_address}}
+      {{form.auth_type}}
     </form>
   </div>
 </div>
diff --git a/tests/app/main/views/test_accept_invite.py b/tests/app/main/views/test_accept_invite.py
index 842466493..aa2f0de30 100644
--- a/tests/app/main/views/test_accept_invite.py
+++ b/tests/app/main/views/test_accept_invite.py
@@ -354,7 +354,7 @@ def test_new_invited_user_verifies_and_added_to_service(
         'password': 'longpassword',
         'mobile_number': '+447890123456',
         'name': 'Invited User',
-        # 'auth_type': 'sms_auth'
+        'auth_type': 'sms_auth'
     }
     response = client.post(url_for('main.register_from_invite'), data=data)
     assert response.status_code == 302
diff --git a/tests/app/main/views/test_register.py b/tests/app/main/views/test_register.py
index 544e69d8c..ca83de216 100644
--- a/tests/app/main/views/test_register.py
+++ b/tests/app/main/views/test_register.py
@@ -327,3 +327,19 @@ def test_cannot_register_with_sms_auth_and_missing_mobile_number(
     err = page.select_one('.error-message')
     assert err.text.strip() == 'Can’t be empty'
     assert err.attrs['data-error-label'] == 'mobile_number'
+
+
+def test_register_from_invite_form_doesnt_show_mobile_number_field_if_email_auth(
+    client,
+    sample_invite
+):
+    sample_invite['auth_type'] = 'email_auth'
+    with client.session_transaction() as session:
+        session['invited_user'] = sample_invite
+
+    response = client.get(url_for('main.register_from_invite'))
+
+    assert response.status_code == 200
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+    assert page.find('input', attrs={'name': 'auth_type'}).attrs['value'] == 'email_auth'
+    assert page.find('input', attrs={'name': 'mobile_number'}) is None