Split Ledger – Easy Group Expense Splitting

Challenge

Managing shared expenses during group trips or events is always a painful problem:

• Entering expenses on Google Sheets via mobile is slow and error-prone
• Receipts and photos are scattered, hard to verify during disputes
• No signal/roaming causes sync interruptions
• End-of-trip settlement is time-consuming and often leads to conflicts

Solution

Built a mobile-first app with offline-first architecture, enabling expense logging in under 10 seconds even without internet. Data is stored locally first, then one-way synced to Google Sheet/Drive when connected. The min-transfers algorithm automatically calculates the optimal payment flow to minimize transactions during settlement.

Key Features

• Quick Expense Entry (under 10 seconds): Optimized VND numpad, one-tap payer and beneficiary selection
• Receipt Capture: Attach photos to expenses, auto-upload to Google Drive
• Smart Settlement: Min-transfers algorithm finds the fewest transactions to balance debts
• Offline-first: Works seamlessly without internet, auto-syncs when connected
• Google Sheet/Drive Sync: Data pushed to Sheets, receipts to Drive folder
• Invite by Code: Generate 6-character code + QR code for friends to join
• Sponsor Support: Track external sponsorship money, excluded from settlement
• Multi-language: Auto-switches between Vietnamese/English based on device locale
• Group Lifecycle: Auto-archive expired groups, settlement reminders

Tech Stack

• Mobile: React Native 0.81+ · Expo 54 · TypeScript (strict) · NativeWind v4
• State: Zustand · react-hook-form + Zod validation
• Database: expo-sqlite · DrizzleORM (type-safe migrations)
• Navigation: expo-router (file-based routing)
• Sync: Google Sheets API · Google Drive API (Direct REST, no SDK)
• Code Quality: Biome (lint/format) · TypeScript strict mode