An invoice app where a duplicate number is impossible
Estimates and invoices from a phone to a PDF in the share sheet — offline, no account.
- PDF templates
- 4 PDF templates
- unit tests on money and numbering
- 46 unit tests on money and numbering
The problem
Freelancers and micro-businesses in the US and Latin America needed invoices without a subscription SaaS: fast, offline, correct numbers, a PDF they can send in seconds.
What we did
- 01
Kept all data on the device in SQLite — no server, no account, instant start.
- 02
Allocated document numbers inside a transaction with a unique index, so duplicates cannot exist at the database level.
- 03
Stored money in integer minor units and tax in basis points, with the arithmetic covered by tests.
Where it landed
A complete iOS product with four PDF templates, three languages, reversible backups and a monetisation policy that can be switched without a release.
Built with
- Expo
- React Native
- SQLite
- Zod
- RevenueCat
Tell us what is not working.
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