Jason Cochran
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Case Study

CoSplit

Overview

CoSplit is a co-parenting expense tracking application designed for separating couples. It provides a simple, focused way to track shared expenses, generate court-ready documentation, and maintain financial transparency without the drama.

Live at: cosplitapp.com

Project Scale

  • Platform: Web application
  • Tech Stack: Next.js + TypeScript + Convex + Better Auth
  • Industry: Family & Legal Tech
  • Architecture: Serverless with real-time sync
  • Target: Co-parents managing shared expenses

Problem Solved

Separating couples face unique challenges tracking shared expenses:

  • No neutral ground: Spreadsheets lead to disagreements
  • Missing documentation: Receipts get lost, memories differ
  • Court preparation: Lawyers need organized records
  • Communication friction: Every expense becomes a negotiation
  • Trust issues: Both parties need visibility

The Solution

CoSplit provides a focused, neutral platform for expense tracking:

  • Quick Logging: Add expenses in seconds with receipt photos
  • Fair Splits: Configurable split ratios (50/50, 60/40, custom)
  • Court-Ready PDFs: Professional exports with all documentation
  • Share Without Signup: Co-parents can view via secure link
  • Approve/Dispute Flow: Clear process for expense validation

Core Features

Expense Management

  • Add expenses with date, amount, category, and description
  • Upload receipt photos for documentation
  • Assign payer and split ratio
  • Track running balances per person
  • Filter and search expense history

Co-Parent Sharing

  • Generate secure shareable links
  • No account required for co-parent
  • View-only access with approve/dispute options
  • Real-time sync when expenses are added
  • Clear status indicators

PDF Export

  • Court-ready expense reports
  • All receipts included
  • Running totals and summaries
  • Professional formatting
  • Perfect for lawyers and mediators

Reimbursement Tracking

  • Request reimbursements for paid expenses
  • Track payment status
  • Settlement history
  • Clear who owes what

Category Management

  • Custom expense categories
  • Default split ratios per category
  • Quick selection when adding expenses
  • Organized expense grouping

Technical Architecture

Real-Time Backend (Convex)

Convex provides the backend infrastructure:

  • Real-time sync: Changes appear instantly for both parties
  • Serverless: Auto-scaling with zero infrastructure management
  • Type safety: End-to-end TypeScript types
  • File storage: Secure receipt image handling

Authentication (Better Auth)

Secure, flexible authentication:

  • Email/Password: Traditional signup flow
  • Google OAuth: One-click login
  • Magic Links: Passwordless option
  • Session management: Secure token handling

Payments (Polar)

Subscription management via Polar:

  • Free tier: 10 expenses to try the platform
  • Pro subscription: Unlimited expenses, full features
  • Webhook integration: Real-time subscription updates

Pricing Model

Free Tier

  • 10 expenses
  • Basic categories
  • Share link with co-parent
  • Limited export

Pro ($5/month or $40/year)

  • Unlimited expenses
  • Receipt photo uploads
  • PDF export for court
  • Reimbursement requests
  • Payment tracking
  • Email notifications

Technical Stack

Frontend

  • Next.js 16: App router with server components
  • TypeScript: Full type safety
  • Tailwind CSS v4: Modern styling
  • Shadcn UI: Accessible component library
  • React Hook Form: Form handling with Zod validation

Backend

  • Convex: Real-time serverless database
  • Better Auth: Authentication via Convex adapter
  • Polar: Subscription and payment processing

Infrastructure

  • Railway: Application hosting
  • Convex Cloud: Database and file storage
  • Google Cloud: OAuth provider

Key Differentiators

Simplicity First

  • No calendar features (not a co-parenting app)
  • No messaging (avoids conflict)
  • Just expenses, splits, and documentation
  • Clean, focused interface

Legal-Ready

  • PDF exports formatted for court
  • Receipt documentation included
  • Clear audit trail
  • Professional presentation

Low Friction

  • Co-parent doesn't need account
  • Quick expense entry
  • Sensible defaults
  • Mobile-optimized

Use Cases

Divorce Proceedings

  • Track all shared expenses during separation
  • Generate reports for lawyers
  • Document reimbursement agreements
  • Maintain financial records

Ongoing Co-Parenting

  • School expenses
  • Medical costs
  • Extracurricular activities
  • Clothing and supplies

Mediation Support

  • Neutral expense tracking
  • Both parties have visibility
  • Clear documentation
  • Reduces conflict

Development Highlights

Clean Architecture

  • Convex queries and mutations
  • Server components with actions
  • Type-safe data layer
  • Organized route groups

Security

  • Authentication on all protected routes
  • User data isolation
  • Secure file uploads
  • Webhook signature verification

User Experience

  • Dark mode support
  • Responsive design
  • Loading states
  • Error handling

Technical Excellence

CoSplit demonstrates proficiency in:

  • Modern Next.js Development: App router, server components, actions
  • Real-Time Applications: Convex for instant sync across devices
  • Authentication Systems: Better Auth with multiple providers
  • Payment Integration: Polar webhooks and subscription management
  • Product Focus: Solving a specific problem without feature bloat

Status: Live in production Website: cosplitapp.com Revenue Model: Freemium SaaS