Bookkeeping Admin

Bookkeeping Admin is a local-first bookkeeping tool for independent professionals and small service businesses in the Netherlands. It covers billing profiles, invoices, expenses, receipts, and quarterly BTW/VAT summaries without requiring a subscription product or a hosted backend.

Why I Built It

I started this project after beginning independent consulting work in the Netherlands and realizing that my bookkeeping workflow felt more complicated than it should. Existing tools were often capable products, but they did not match the experience I wanted: some felt too advanced, some too limited, some visually uninspiring, and many required an ongoing subscription.

I wanted something simpler, more focused, and more aligned with my own way of working. I also wanted to use the project to demonstrate a practical AI-assisted delivery workflow: as a PM, I used OpenAI and Codex to shape requirements, iterate on UX details, and ship a working product that I can continue improving.

Product Positioning

This is intentionally not a full accounting platform.

The current version is designed around a narrower idea:

• local-first bookkeeping
• privacy-conscious by default
• no required account creation
• no hosted user database
• focused workflows for solo operators and small service businesses

That tradeoff keeps the product lightweight, inexpensive to run, and well scoped as a portfolio project.

Features

• Home: quick access to the main flows
• Invoices: build invoices from saved profiles, calculate VAT from hours and rate, export a one-page PDF, and manage everything in a sortable table with paid/overdue status
• Profiles: reusable sender and client billing details, including a letterhead
• Expenses: log costs, VAT rates and receipts, filtered by year
• VAT Summary: net BTW per quarter, with each quarter markable as filed and paid so the headline shows what is still owed
• Finance: import a bank CSV from one or more accounts and see where the money comes from and goes, what is a fixed commitment versus flexible spending, and where the year lands. Money moved between your own accounts is never counted as either, and the figures reconcile against the balance your bank printed — parsed in the browser, never uploaded
• Belastingdienst: the whole tax year — receivables, VAT, an income tax estimate with every step shown, and a projection to 31 December
• Language: full NL/EN switch; English shows Dutch tax terms alongside, since those are the words on the actual forms
• Theme: light and dark, following your system by default with a manual override
• Settings: passphrase and recovery code, auto-lock, bank accounts, backup and restore, AI import
• Encryption: set a passphrase and everything in the browser is encrypted at rest — see docs/SECURITY.md
• Local persistence: everything stored in browser localStorage
• Backup & restore: export all data to JSON, and merge or replace it back

Data Safety

Encryption

Setting a passphrase encrypts everything stored in the browser. A random data key encrypts the records, and that key is wrapped separately by your passphrase and by a recovery code, so either opens the vault and neither can be derived from the other. Nothing stores the passphrase, the recovery code or the data key — which is why there is no password reset, and cannot be one.

The design, its parameters, and an honest account of what it does not protect against are in docs/SECURITY.md.

It is opt-in: the app is fully usable without a passphrase, because switching it on is irreversible in the way that matters. Lose both the passphrase and the recovery code and the data is gone.

Everything else

All data lives in this browser's localStorage and nowhere else. That keeps the app private and backend-free, but it also means clearing site data, switching browsers or using a different browser profile will lose everything.

• Export a backup from the dashboard regularly; it downloads a single JSON file.
• Restoring offers Merge, which only adds entries that are not already present and never overwrites or removes what is already there, and Replace, which downloads a safety backup of the current data before overwriting it.
• A restore is applied under a rollback guard: if any write fails, every key is put back as it was, so a failed restore cannot leave the books half-updated.
• Receipts are stored inline as base64, and the whole origin is limited to roughly 5MB, so single receipt files are capped at 1MB.

An optional public/seed/backfill.json (gitignored) is applied once on first load, so a prepared set of books can be loaded without hand entry. It holds real bookkeeping data and must never be committed.

Bank statements are parsed in the browser and stored locally like everything else; nothing is uploaded. The free-text notification field is dropped on import because it carries partial card numbers. *.csv is gitignored so an export cannot be committed by accident.

The AI import panel currently keeps its API key in localStorage. That is acceptable on a personal machine and not acceptable hosted — moving extraction behind a server route is a prerequisite for launch.

BTW figures do not model reverse-charge (BTW verlegd), the small business scheme (KOR) or intra-EU supplies, and the income tax estimate ships with editable default rates that should be checked against belastingdienst.nl. Neither is tax advice.

Screenshots

All figures below are fictional demo data, not real bookkeeping.

Home

Quick access to the main flows, with backup and AI-assisted import below.

Invoices

Saved invoices as a sortable table: select rows to download their PDFs in bulk, mark paid inline, and read the column totals in the closing row.

Finance

Import a bank statement and the year is laid out: where money comes from and where it goes, what is a fixed commitment versus flexible spending, and where 31 December lands. Clicking any figure opens the transactions behind it. What the rules cannot place is grouped by merchant, so one decision files every transaction from it.

The screenshot predates the income panel added later.

Belastingdienst

The tax year in one view — receivables, net VAT per quarter, and a projection to 31 December with the income tax estimate broken down step by step. Shown in dark mode; the app follows your system setting and can be overridden.

Project Structure

.
├── app/
│   ├── belastingdienst/page.tsx  Tax year overview, charts, income tax estimate
│   ├── btw-summary/page.tsx      Quarterly VAT, with settled-quarter tracking
│   ├── clients/page.tsx          Billing profile management
│   ├── expenses/page.tsx         Expense and receipt tracking
│   ├── finance/page.tsx          Bank import, income and spending, year projection
│   ├── invoices/page.tsx         Invoice builder, preview and PDF export
│   ├── settings/page.tsx         Passphrase, backups, AI import
│   ├── components/
│   │   ├── AiImportPanel.tsx     AI-assisted import (preview; provider not wired)
│   │   ├── BackupPanel.tsx       Export / restore bookkeeping data
│   │   ├── ConfirmDelete.tsx     Confirmation that can be switched off for good
│   │   ├── InvoiceTable.tsx      Sortable invoice table with row actions
│   │   ├── NavTabs.tsx           Navigation and language control
│   │   ├── SeedLoader.tsx        One-time local backfill from /seed
│   │   ├── ThemeToggle.tsx       Light / dark / system
│   │   ├── TransactionDrawer.tsx Paged list behind a figure
│   │   ├── VaultGate.tsx         Lock screen, setup, recovery code, auto-lock
│   │   ├── VaultSettings.tsx     Change passphrase, reissue code, turn off
│   │   └── charts.tsx            Inline SVG donut, bars and projection
│   ├── not-found.tsx             404
│   ├── layout.tsx                Shared app shell
│   ├── page.tsx                  Home
│   └── globals.css               Design tokens for light and dark
├── docs/
│   ├── OPEN-ITEMS.md             Engineering debt and blockers
│   └── SECURITY.md               How the encryption works, and what it does not do
├── lib/
│   ├── ai-import.ts              Extraction contract and provider seam
│   ├── backup.ts                 Backup export, validation and restore
│   ├── bank.ts                   Bank CSV parsing, dedupe and merge
│   ├── billing.ts                Shared billing types and money helpers
│   ├── categories.ts             Spending categories and the rules that assign them
│   ├── crypto.ts                 Vault cryptography
│   ├── crypto.test.ts            Tests for it
│   ├── finance.ts                Spending aggregation, recurrence, projection
│   ├── i18n.ts                   NL/EN dictionary
│   ├── local-storage.ts          Storage hook, vault-aware
│   ├── tax.ts                    ZZP income tax estimate and BTW deadlines
│   └── vault.ts                  In-memory vault, migration, lock/unlock
├── public/                       Static assets
└── README.md

Tech Stack

Layer	Technology	Purpose
App framework	Next.js 16	App shell, routing, build tooling
UI	React 19	Client-side UI and stateful forms
Language	TypeScript	Type safety across app logic
Styling	Tailwind CSS 4	Layout and visual styling
Persistence	localStorage	Local-first data storage in the browser
Encryption	WebCrypto	AES-GCM and PBKDF2 from the platform; no dependency handles keys
Tests	node:test	Built in; Node runs the TypeScript directly, no test framework
Charts	inline SVG	No charting dependency; colours validated for contrast and colourblind separation
Tooling	ESLint	Basic code quality checks

Built With AI

This project is also a practical exploration of AI-assisted product development.

I used AI assistants (initially OpenAI and Codex, more recently Claude Code) to:

• turn rough bookkeeping pain points into product requirements
• define the page split and information architecture
• iterate on invoice, profile, and VAT workflows
• refine form behavior and reusable data models
• review product tradeoffs around privacy, local-first storage, validation, and security
• find and fix real defects: a silent data-loss bug in the storage layer, a VAT summary that only counted half a return, and a timezone bug that reported a filing deadline a day early

The goal was not just to generate code, but to use AI as part of a real product delivery workflow: moving from a personal problem to a working, testable product.

Privacy And Scope

This version does not use a backend database. Data is stored locally in the browser/device running the app.

That means:

• no central user data storage
• no authentication layer in the current version
• no multi-device sync
• no responsibility for hosting other users' bookkeeping data

For this stage of the project, that is a deliberate product choice rather than a missing feature.

Running The Project

Install dependencies and start the development server:

npm install
npm run dev

Open http://localhost:3000 in your browser.

Available scripts:

npm run dev
npm run lint
npm run build
npm run start
npm test      # the vault crypto tests

Deployment

The simplest deployment path is Vercel. The app works well as a public demo because it does not depend on a backend database in its current form.

Roadmap

Done

• Encryption at rest. A passphrase encrypts everything in the browser, with a recovery code as the only way back in. docs/SECURITY.md.
• Bank import. CSV from Dutch banks, categorised, with recurring direct debits recognised as fixed commitments regardless of category.

Next, in this order

1. Sync, encrypted end to end. The vault is local, so laptop and phone are still separate islands and moving between them means exporting and restoring a file by hand. The encrypted blob is already the right shape to sync; what is missing is somewhere to put it and an account identity to put it under. The server would hold ciphertext it cannot read, which is the only version of sync consistent with how this app treats data. Needs a decision on storage, and it is the first thing here to require a service account.

2. AI import. Extraction moves behind a server route so the API key never sits in the browser, closing the standing security gap. That unlocks categorising the long tail of small local merchants no rule list can cover, and PDF statements. Second because an AI feature on an app with no accounts is the roof before the walls.

3. Then: MT940/CAMT imports, matching bank transactions against invoices so unpaid work reconciles itself, the business/private flag that pushes a deductible cost straight into the tax picture, and multiple line items per invoice.

Known rough edges

The lock and setup screens are functional rather than designed, there is no passphrase strength hint, and errors are plain red text. Listed here rather than quietly left, because they are the first thing anyone else would meet.

Where this is heading: personal financial admin, not just bookkeeping

Invoices and BTW are one corner of a freelancer's finances. The same local-first, privacy-conscious foundation extends naturally to the rest of it, as separate tabs over a shared ledger:

• Bank statements — ✅ CSV import works today, parsed in the browser. Still to do: MT940/CAMT, PDF statements, and matching transactions against invoices so unpaid work reconciles itself.
• Expense intelligence — ✅ categorisation ships with rules covering roughly 93% of value on a real statement. Still to do: the business/private flag that would push a deductible cost straight into the tax picture, and AI for the long tail of small local merchants that no rule list can cover.
• Mortgage and debt — hold the mortgage, its rate and remaining term; show interest paid per year, which feeds the income tax picture (eigenwoningforfait, mortgage interest deduction).
• Net worth — assets and liabilities in one place, including box 3 holdings, with the same year-by-year treatment the tax page already applies to income.
• Forward view — extend the existing projection from revenue into full cash flow: what is coming in, what is committed, what to keep aside, and what is genuinely free.

Two principles should survive that expansion. Nothing is invented — an estimate is always shown with the arithmetic behind it, as the income tax breakdown already is. And anything sensitive stays on the user's machine unless they explicitly choose otherwise; a hosted version needs a real backend and auth story before it holds anyone's bank data.

If it grows beyond local-first

Encryption landed first, deliberately: it means a backend can be added later without the server ever being able to read what it stores. What is still missing is the storage itself and an account identity — see "Next" above.

Portfolio Value

This project demonstrates:

• identifying a real user problem from personal experience
• scoping an MVP around a focused use case
• making explicit tradeoffs about privacy, complexity, and cost
• using AI tools to accelerate delivery
• shipping a working interface instead of stopping at a spec or concept

Status

Bookkeeping Admin is an active portfolio and learning project. The current version is usable as a local-first bookkeeping tool and will continue to evolve through iterative improvements.

Small improvements and documentation updates are committed as the product evolves.