TaxMeter — Case Study · Karolina Bittman

01 — The problem

One income. Five tax authorities. Zero visibility.

Every self-employed person in Canton Zürich pays into five separate systems — each with its own rates, brackets and municipal multipliers. Most freelancers guess how much to set aside, and guess wrong.

Invoicing means paying CHF 30+/month for Bexio. Expense tracking is a separate tool. Tax estimation is a Treuhänder or a spreadsheet. Nothing combines all three affordably — and privately.

AHV / IV / EO sliding scale Cantonal tax progressive Municipal tax Steuerfuss 90–124% Federal tax progressive Church tax optional

02 — The solution

Four tools, one app. All on your phone.

The Solaris orb is the heart of it: a live tax reserve that recalculates with every invoice and receipt, across 25+ Zürich municipalities. It glows teal when you're fully covered — tax awareness becomes passive.

TOOL·01

Tax Meter

Real-time reserve calculator covering AHV/IV/EO (incl. sliding scale), cantonal, municipal, federal and church tax for 25+ municipalities.

TOOL·02

Bill Buster

Scan your provisional Steuerrechnung, compare it against actual year-to-date income, and auto-generate a formal Einsprache in German if you've been overcharged.

TOOL·03

QR Invoicing

Swiss QR-bills to the SIX SPS v2.3 standard in one tap. Mark an invoice paid and the revenue flows straight into the tax calculation.

TOOL·04

Expense Tracking

Photograph a receipt; on-device OCR extracts merchant, amount and date. Deductions update the reserve instantly.

03 — Design identity

Deliberately anti-tax-software.

Near-black canvas, one hero accent, and a strict typographic rule: when you see monospaced text, it's money.

The orb doubles as data display and emotional indicator. Colour went through three iterations — the shift from navy to near-black came from seeing it on a real device, not from a prompt. The app ships in both light and dark mode.

TaxMeter expenses screen in dark mode with category filters and receipt scan button

#0C0F1ABackground

#4ECDC4Teal · safe / primary

#CD5B5BCoral · expenses

#F5A623Amber · warnings

#9B7FB8Mauve · low state

#F0F0F5Primary text

General Sans

Display & interface

IBM Plex Mono — 10,500.00

Every financial number

04 — Architecture

Zero backend. That's the product.

No servers, no cloud database, no accounts, no analytics SDKs. Everything runs on-device with SQLite — so the App Store privacy label reads “Data Not Collected.” Almost no finance app can claim that.

The tax engine is pure TypeScript with zero dependencies, validated by 29 unit tests. Privacy wasn't a compromise; it's the positioning.

React Native + Expo SDK 54 TypeScript strict SQLite expo-sqlite ML Kit on-device OCR swissqrbill Zustand Face ID local auth

TaxMeter security onboarding screen: your data stays on your phone, no cloud, no tracking

05 — The hardest bug

A QR-bill vs. a real bank.

The QR-bill passed every internal test — then Raiffeisen's validator rejected it against three spec violations. Fixing it meant restructuring the address model across settings, onboarding and invoice creation, plus a pre-flight gate that blocks a broken bill before it ever reaches a client.

This is the detail that proves the app was built against a real standard, not a mock.

TaxMeter new invoice form with structured street, building number, postal code and town fields

swiss-qr-validator · SIX SPS v2.3raiffeisen.ch

FAIL

Creditor address incomplete — combined address lines rejected; structured street / building / postal / town required.

FAIL

Debtor address incomplete — same structural requirement on the payer side.

FAIL

Invalid reference type — SCOR with a non-RF string on a normal IBAN.

FIXED

Structured address model across settings, onboarding and invoicing · QRR for QR-IBANs, NON for standard IBANs · pre-flight validation gate before export.

06 — Process

AI-assisted. Human-directed.

Claude for strategy, tax-law research and architecture. Pencil.dev for twelve wireframed screens. Claude Code for implementation. Expo and Xcode for on-device testing.

Scope was deliberately cut from four cantons to one — Zürich with verified, accurate data beats four done with guesswork. AI moved implementation at high speed, but every product decision, design judgement and quality bar came from a human reviewing it on a real screen.

Outcome

Shipped, tested, submitted.

passing tax-engine tests, zero TypeScript errors

Zürich municipalities with verified Steuerfüsse

languages — bilingual App Store listing & site (DE + EN)

on-device — “Data Not Collected” privacy label

Functional iOS app submitted to the App Store · marketing site live at taxmeter.ch · full custom screenshot set in both languages.

Reflection

“AI writes the code. Humans make the decisions.”

This project tested whether a designer could ship a production-quality native app, a marketing site and a compliant Swiss financial tool solo, using AI tools — all the way to the App Store. The answer was yes, with a caveat: the value wasn't the code generation. It was the product thinking, the design judgement, and the willingness to test against reality — a real bank, a real device, a real tax table.