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Bir Finans

A finance core that is exact to the last kuruş.

System
Work, ledger & finance management
Client
Our own operations
Status
In internal use
Scope
Product design, financial modelling, engineering
Field
Corporate

Bir Finans · demo

Bir Finans — Work, ledger & finance management
Bir Finans mobil

Bir Finans · demo

Bir Finans

Screens are taken from a demo copy running on sample data; they contain no real customer data.

01 — Problem

For retainer clients, monthly packages, quota usage, extra work and revisions — along with collections, cheques, bank movements and VAT — were tracked in different places. Period close and client balances were calculated by hand every month.

02 — System

We built a work and finance application on a double-entry ledger in which every money record must balance debit against credit. Corrections are made by reversal, never deletion; amounts are stored as exact decimals, and foreign-currency documents post to the TRY ledger with TCMB rates and FX differences.

Period close

Every step from work entry to collection leaves a balanced ledger record.

  1. 01Work entry
  2. 02Quota calc
  3. 03Period close
  4. 04Receivable
  5. 05Collection

Correction → reversal entry

Bir Finans

Accounts

Work entry

Quota calc

Period close

Receivable

Collection

Schematic · admin panel

03 — Architecture

The Next.js interface talks to a NestJS API over server-side sessions. Money POSTs carry idempotency keys, period close takes row locks, and every change lands in an audit log.

Bir FinansSystem architectureREV · 2026
  1. L0Users
    • Owner
    • Admin
    • Staff
    • Viewer
  2. L1Interfaces
    • Web app · PWA
    • Reconciliation link
  3. L2Application
    • NestJS 10
    • Prisma 6
    • Audit log
  4. L3Modules
    • Ledger
    • Accounts
    • Documents
    • Cash & bank
    • Cheques & notes
    • Quota engine
    • Reports
  5. L4Data
    • PostgreSQL 16
    • DECIMAL(19,4)
  6. L5External services
    • TCMB rate feed

04 — Capabilities

  1. 01

    Double-entry ledger

    No transaction is saved unless debit equals credit; typed accounts, a dedicated VAT account and void-by-reversal instead of deletion.

  2. 02

    Current accounts

    Customer, supplier, person and institution accounts; VKN/TCKN checksum validation, risk levels, Excel import/export, statements and netting/transfers.

  3. 03

    Documents

    Sales/purchase invoices, returns and quotes; line and document discounts, VAT inclusive/exclusive, numbering series, quote-to-invoice conversion and recurring documents.

  4. 04

    Cash, bank, cheques

    Statement import and matching that understands Turkish bank formats, cash counts; a full cheque and note lifecycle from portfolio to collection, endorsement or bounce, and a cheque calendar.

  5. 05

    Quota and period engine

    Contracts with price-version history, package/extra/hourly pricing, quota and revision overage; monthly period close and reopen with reason and audit.

  6. 06

    Reconciliation and reports

    A tokenised reconciliation page clients can agree to or dispute; aging, profit & loss, VAT, cash and audit reports in PDF and Excel.

05 — Impact

  • 01

    Period close and balance calculation for retainer clients are handled by the app.

  • 02

    Nothing is deleted; every correction is traceable in the ledger.

19,4
decimal precision
42
data models
~90
application screens
~293
test cases

Technology stack

Frontend

  • Next.js 15.5
  • React 19
  • TanStack Query
  • Radix UI

Backend

  • NestJS 10
  • Prisma 6
  • Zod
  • decimal.js

Data

  • PostgreSQL 16

Documents

  • Puppeteer
  • ExcelJS

Infrastructure

  • Docker Compose
  • nginx
  • Playwright
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