diff --git a/DEMO_DATA.md b/DEMO_DATA.md
index 8b90ae1..b01aedf 100644
--- a/DEMO_DATA.md
+++ b/DEMO_DATA.md
@@ -3,6 +3,14 @@
 Seeded directly against the live Supabase backend (not through the UI) for
 speed. All accounts share the password `DemoPassword123!`.
 
+**Demo Neighbourhood join code: `ALFALAH`** — "Masjid Al-Falah Kariah",
+already joined by all 5 demo owners below. Sign in as any of them, go to
+Family → Neighbourhood, and the board is already populated (see
+[Demo Neighbourhood](#demo-neighbourhood--masjid-al-falah-kariah) below for
+what's seeded). To join from a *fresh* (non-demo) account instead, use
+Family → Neighbourhood → "+ Join or start another neighbourhood" → enter
+`ALFALAH`.
+
 ## Families
 
 | Family | Owner login | Assets | Coverage | Notable features |