--- title: "Intelligent Accounting SaaS Platform" description: "Full-stack SaaS platform for accounting, tax management, and financial intelligence - designed for small businesses." locale: "en" canonical: "https://portfolio.josedacosta.info/en/achievements/plateforme-comptabilite-saas" source: "https://portfolio.josedacosta.info/en/achievements/plateforme-comptabilite-saas.md" html_source: "https://portfolio.josedacosta.info/en/achievements/plateforme-comptabilite-saas" author: "José DA COSTA" date: "2025" type: "achievement" slug: "plateforme-comptabilite-saas" tags: ["Next.js 16", "TypeScript", "Prisma", "PostgreSQL", "Better Auth", "AI SDK", "Open Banking", "Stripe"] generated_at: "2026-04-23T15:45:29.465Z" --- # Intelligent Accounting SaaS Platform Full-stack SaaS platform for accounting, tax management, and financial intelligence - designed for small businesses. **Date:** January 2025 - March 2026 **Duration:** 14 months **Role:** Founder & CTO - Solo Developer **Technologies:** Next.js 16, TypeScript, Prisma, PostgreSQL, Better Auth, AI SDK, Open Banking, Stripe ### Key Metrics - Lines of Code: **-** - TypeScript, React, CSS - Features: **-** - Autonomous modules - API Routes: **-** - REST endpoints - Database Models: **-** - Prisma schema models ## Presentation _Project definition and scope_ ### Domain Accounting, taxation, financial management, legal obligations for French businesses (PCG, CGI, Code de commerce) ### Target Users SMB directors (B2B), chartered accountants, accounting collaborators - with 6 differentiated roles (Admin, Collaborator, Viewer, Accountant, Accounting, Banking) **Content:** The **Intelligent Accounting SaaS Platform** is a comprehensive, full-stack web application designed for **French SMBs and freelancers**. It covers the complete spectrum of accounting, tax management, and financial operations that a company must perform to stay legally compliant in France. Born from a concrète need - managing the accounting of **ACCENSEO**, a software consulting company. **Domain:** Domain **Target Users:** Target Users **Functional Scope:** Functional Scope **Scope Banking:** Banking & Open Banking **Scope Invoicing:** Invoicing (Sales & Purchases) **Scope Tax:** Tax Declarations (TVA, IS, CFE...) **Scope Accounting:** Accounting Entries & FEC **Scope A I:** AI-Powered Assistant **Scope Reconciliation:** Bank Reconciliation **Scope Documents:** Document Management & OCR **Scope Reporting:** Financial Reporting & Forecasts **Scope Einvoicing:** E-invoicing (DGFIP v3.1) ## Objectives, Context, Stakes & Risks _Strategic vision and constraints_ ### Context The project builds upon a **thorough analysis of existing accounting solutions**: saved web pages, intercepted API responses (JSON files), extracted JavaScript source code, and systematic screenshots. A **security audit** of competing platforms was conducted, identifying several vulnerabilities (IDOR, KYC issues) - this audit informed the secure design of the platform. A **market study of accounting software** was conducted, alongside research on **Open Banking PSD2** and banking aggregators to choose integration providers. Documentation on electronic invoicing platforms (PDP) was also assembled. ### Stake Autonomy Enable ACCENSEO to operate without external accounting provider ### Stake Compliance Meet all filing obligations of a SAS under IS regime, simplified real TVA regime ### Stake Einvoicing Anticipate the French 2026-2027 e-invoicing mandate to avoid any last-minute catch-up - Build a complete accounting platform to autonomously manage ACCENSEO accounting - Automate all tax obligations: TVA (CA3), IS, CFE, CVAE, DAS2, PAS - with EDI submission via Teledec - Integrate Open Banking for automatic bank transaction synchronization (Nordigen/GoCardless, Bridge, Qonto) - Provide an AI layer to assist users with categorization, document analysis, and accounting/tax questions - Build a reusable codebase potentially commercializable as a standalone SaaS **Objectives:** Objectives **Context:** Context **Stakes:** Business Stakes **Stake Autonomy:** Accounting Autonomy **Stake Compliance:** Tax Compliance **Stake Einvoicing:** E-invoicing Ready **Risks:** Identified Risks **Risk1 Title:** Regulatory Complexity **Risk1 Desc:** French accounting is extremely regulated (PCG, CGI, Code de commerce). Any error in tax calculations can have direct financial consequences. **Risk2 Title:** Maintenance Burden **Risk2 Desc:** With 234,000 lines of code and 91 database models, the project reaches a considerable size for a solo developer. Long-term maintenance requires rigorous architecture. **Risk3 Title:** Regulatory Obsolescence **Risk3 Desc:** Tax rules change regularly (TVA rates, IS thresholds, e-invoicing planned for 2026-2027). The platform must be designed for easy adaptation. ## The Steps - What I Did _Chronological phases and personal contributions_ - Ideation & Market Research - Architecture & Technical Setup - Core Feature Development - Advanced Features **Phase1 Period:** Early 2025 **Phase2 Period:** Q1 2025 **Phase3 Period:** Q2 2025 - Q4 2025 **Phase4 Period:** Q1 2026 ## Actors & Interactions _Team, stakeholders, and collaboration dynamics_ ### José DA COSTA - Direction & Expertise (~15-20%) - Product vision and feature prioritization across the accounting and tax scope - Accounting/tax domain expertise (PCG, CGI, TVA, IS, CFE, DAS2) - Detailed functional specifications and instruction prompts for each feature - Manual code review on every generated file - logic, naming, security - Writing verification scripts to validate accounting calculations and tax rules - Systematic regression testing after each iteration - Security audit of competing platforms - Open Banking and e-invoicing regulatory research ### Claude Code (AI) - Implementation (~80-85%) - TypeScript/React/Next.js code generation across the full stack - 42 feature modules with full CRUD and business logic - 382 API routes with validation and error handling - Prisma schema with 91 models and 63 enums - Third-party API integration (Stripe, Open Banking, EDI) - UI components with shadcn/ui and responsive layouts **Human Essential Text:** This project was built as a **human + AI duo**. The human developer directs the AI through detailed prompts to generate production-grade code for a complex accounting platform. An accounting platform handles **regulated financial data** - tax calculations, bank reconciliations, legal declarations. The AI generates code fast, but it cannot understand **French tax law** (CGI, PCG), validate **accounting accuracy**, or make **product decisions** about what to build. Every feature required **deep domain expertise** to specify correctly and **rigorous verification** to avoid financial errors. **Stakeholders:** External Stakeholders **Workflow:** Iterative Development Workflow **Wf Inspiration:** Inspired by SDD methodologies: Spec Kit, OpenSpec, BMAD, Kiro (AWS) & Tessl ## Results _Impact for myself and for the company_ **Codebase Metrics:** Codebase Metrics **Feature Dist:** Feature Distribution (42 Features) **Comparison:** Feature Coverage Analysis **Db Dist:** Database Model Distribution (91 Models + 63 Enums) **Effort Dist:** Development Effort Distribution **For Me:** For Me - Skills Acquired & Reinforced **Technical Skills:** Technical Skills **Domain Skills:** Accounting & Tax Domain **For Company:** For the Company - Business Impact **Delivered Features:** **Delivered Features Summary:** - **Accounting & Entries**: Chart of accounts (general, auxiliary, analytical), journals, entries (sales, purchases, bank), general ledger, trial balance, bank reconciliation, FEC (generation, controls, history), closing entries - **Banking**: Multi-bank connections (Nordigen, Bridge, Qonto), automatic transaction sync, AI-assisted categorization, receipt management, invoice-transaction reconciliation - **Invoicing**: Sales invoices (draft, pending, overdue, collected, cancelled), quotes (draft, sent, accepted, declined, invoiced, expired), purchase invoices, PDF generation, credit notes, e-invoicing - **Tax**: TVA (CA3 monthly/quarterly + simulation), IS (instalments + balance), CFE, CVAE, DAS2, PAS, salary tax, RCM 2777, tax calendar, EDI e-filing via Teledec, Chrome extension for impots.gouv.fr - **AI**: Accounting/tax chat assistant (3 providers), contextual help with detail levels, document analysis with structured extraction (Zod schemas) ## Project Aftermath _What happened after delivery and current state_ **Content:** **Immediate Future**: The platform is still under **active development** as of March 2026. The latest source file modifications date from March 12, 2026 (API collaborator routes). The focus is on stabilizing core features and preparing for production usage. **Medium-Term Trajectory**: Several strategic directions are being explored: - **Production deployment** for ACCENSEO's own accounting needs - **Electronic invoicing readiness** for the upcoming French 2026-2027 mandate - comprehensive PDP documentation (DGFIP v3.1 specifications, semantic annexes, feasibility studies) is already prepared - **Potential SaaS commercialization** - the Feature-Driven architecture with 42 autonomous modules was designed from the start to support multi-tenant operation The Feature-Driven approach ensures new modules can be added independently without impacting existing functionality, and the multi-provider AI strategy protects against vendor lock-in. ## Critical Reflection _Retrospective analysis and lessons learned_ ### Would Do Differently - **Regular commits from day one** to preserve an exploitable history and enable safe rollbacks - **Tests from the start** (TDD or at minimum tests for tax calculation functions) - the most critical business logic should have been tested as it was written - **Automatic API documentation** (Swagger/OpenAPI) for the 382 routes - this would facilitate future developer onboarding and API consumption **Strengths:** Strengths **Improvements:** Areas for Improvement **Would Do Differently:** What I Would Do Differently **Lessons:** Lasting Lessons