diff --git a/lib/invites_repo.rb b/lib/invites_repo.rb
index dac00bd6a91929d2f8aeeca01640cf25a53021d3..023a06bb4aad43c5722f3dc63db0c198e99a3d09 100644
--- a/lib/invites_repo.rb
+++ b/lib/invites_repo.rb
@@ -135,8 +135,12 @@ protected
 	def invalid_code(customer_id, code)
 		@redis.incr("jmp_invite_tries-#{customer_id}").then {
 			@redis.expire("jmp_invite_tries-#{customer_id}", 60 * 60)
-		}.then do
+		}.then {
+			@redis.hexists("jmp_group_codes", code)
+		}.then { |is_group|
+			raise Invalid, "#{code} is a post-payment referral" if is_group.to_i == 1
+
 			raise Invalid, "Not a valid invite code: #{code}"
-		end
+		}
 	end
 end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 6978753ce6f61ab9a9cb3b87106207ef632cf146..8aec8f80932d69d83a474e838522e7961d414097 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -257,6 +257,10 @@ class FakeRedis
 		@values.dig(key, field)
 	end
 
+	def hexists(key, field)
+		hget(key, field).nil? ? 0 : 1
+	end
+
 	def hincrby(key, field, incrby)
 		@values[key] ||= {}
 		@values[key][field] ||= 0
diff --git a/test/test_registration.rb b/test/test_registration.rb
index 1fe64ca87dd070cdd0c26d1a703eb1f19f0e743b..1b194c0c8a4e47e31b8eb4227ed5fd2efbbf170e 100644
--- a/test/test_registration.rb
+++ b/test/test_registration.rb
@@ -736,6 +736,11 @@ class RegistrationTest < Minitest::Test
 						EMPromise.resolve(nil),
 						["jmp_invite_tries-test", 60 * 60]
 					)
+					Registration::Payment::InviteCode::REDIS.expect(
+						:hexists,
+						EMPromise.resolve(0),
+						["jmp_group_codes", "abc"]
+					)
 					Command::COMMAND_MANAGER.expect(
 						:write,
 						EMPromise.resolve(
@@ -772,6 +777,74 @@ class RegistrationTest < Minitest::Test
 			end
 			em :test_write_bad_code
 
+			def test_write_group_code
+				result = execute_command do
+					customer = customer(plan_name: "test_usd")
+					Registration::Payment::InviteCode::REDIS.expect(
+						:get,
+						EMPromise.resolve(0),
+						["jmp_invite_tries-test"]
+					)
+					Registration::Payment::InviteCode::DB.expect(
+						:transaction,
+						[]
+					) { |&blk| blk.call }
+					Registration::Payment::InviteCode::DB.expect(
+						:exec,
+						OpenStruct.new(cmd_tuples: 0),
+						[String, ["test", "abc"]]
+					)
+					Registration::Payment::InviteCode::REDIS.expect(
+						:incr,
+						EMPromise.resolve(nil),
+						["jmp_invite_tries-test"]
+					)
+					Registration::Payment::InviteCode::REDIS.expect(
+						:expire,
+						EMPromise.resolve(nil),
+						["jmp_invite_tries-test", 60 * 60]
+					)
+					Registration::Payment::InviteCode::REDIS.expect(
+						:hexists,
+						EMPromise.resolve(1),
+						["jmp_group_codes", "abc"]
+					)
+					Command::COMMAND_MANAGER.expect(
+						:write,
+						EMPromise.resolve(
+							Blather::Stanza::Iq::Command.new.tap { |iq|
+								iq.form.fields = [{ var: "code", value: "abc" }]
+							}
+						),
+						[Matching.new do |reply|
+							assert_equal :form, reply.form.type
+							assert_nil reply.form.instructions
+						end]
+					)
+					Command::COMMAND_MANAGER.expect(
+						:write,
+						EMPromise.reject(:test_result),
+						[Matching.new do |reply|
+							assert_equal :form, reply.form.type
+							assert_equal(
+								"abc is a post-payment referral",
+								reply.form.instructions
+							)
+						end]
+					)
+
+					Registration::Payment::InviteCode.new(
+						customer,
+						"+15555550000"
+					).write.catch { |e| e }
+				end
+				assert_equal :test_result, result
+				assert_mock Command::COMMAND_MANAGER
+				assert_mock Registration::Payment::InviteCode::DB
+				assert_mock Registration::Payment::InviteCode::REDIS
+			end
+			em :test_write_group_code
+
 			def test_write_bad_code_over_limit
 				result = execute_command do
 					customer = customer(plan_name: "test_usd")