Household Group Creation & Invite

A user can create a household group (max 5 members) and invite roommates via a shareable link or email. Invitees can join without mandatory account creation for the first session (guest mode via magic link), reducing onboarding friction.

Quick Expense Entry

Adding an expense must take under 10 seconds: enter amount, description, select who paid, and select who it's split among. Default split is equal among all members. The form must be accessible from a persistent floating action button on all screens.

Flexible Split Rules

Each expense can be split by: (a) equal shares, (b) exact fixed amounts per person, (c) percentage-based allocation, or (d) custom shares/weights. The selected rule is remembered as the default for that expense category.

Month-End Settlement Summary with Minimum Transactions

At any point (and auto-generated at month-end), the app computes and displays the minimum number of transactions required to fully settle all balances across the group, using a debt-simplification algorithm (e.g., greedy net-balance matching). Each suggested transaction shows payer, receiver, and exact amount.

Real-Time Sync via Supabase Realtime

All expense additions, edits, and deletions are broadcast to all connected group members instantly via Supabase Realtime subscriptions (PostgreSQL change notifications). No manual refresh required — balances and expense lists update live.

Expense Categories & Tags

Users can assign a category to each expense from a predefined list (Rent, Utilities, Groceries, Dining, Subscriptions, Transport, Household, Other) with optional free-text tags. Categories are used for monthly breakdown charts.

Recurring Expense Support

Users can mark an expense as recurring (monthly) with a set day of month. The app auto-creates the expense entry each month via a Supabase Edge Function cron job, with a push notification to all members for confirmation.

Push Notifications & Settlement Reminders

Members receive push notifications (via Web Push API / service worker) when: a new expense is added, they are tagged in an expense, a settlement is requested, and 3 days before month-end if unsettled balances exist. Notification preferences are user-configurable.

Payment App Deep Links

On the settlement summary screen, each suggested transaction includes one-tap deep links to Venmo, PayPal, and Zelle pre-populated with the recipient and amount, reducing friction to zero for the actual payment step.

Monthly Expense History & Audit Log

All expenses are stored with full history. Users can browse by month, filter by category or member, and see a timeline of all additions and edits. Deleted expenses are soft-deleted and visible to admins for dispute resolution.

Receipt Photo Capture & Storage

Users can attach a photo of a receipt to any expense using device camera or file upload. Images are stored in Supabase Storage. Thumbnail is shown inline in the expense list; full image is viewable on tap.

Performance — Sub-2s Page Load

All primary screens (dashboard, expense list, add expense form, settlement summary) must achieve a Time to Interactive (TTI) under 2 seconds on a standard 4G connection. Achieved via Next.js 15 Server Components, edge caching on Vercel, and optimistic UI updates.

Mobile-First Responsive UI

The app must be fully usable on mobile browsers (375px viewport and up) without a native app install, following a mobile-first design approach with Tailwind CSS. Touch targets must be ≥44px. The app should be installable as a PWA.

Secure Auth with Row-Level Security

Authentication via Supabase Auth (email magic link + Google OAuth). All database tables enforce Row-Level Security (RLS) policies ensuring users can only read/write data belonging to their household group. No cross-group data leakage is permissible.

CSV / PDF Monthly Export

Any member can export the current month's expenses as a CSV (for spreadsheet import) or a formatted PDF summary (for record-keeping or landlord documentation), generated server-side via a Supabase Edge Function.