Why I Use TypeScript for Anything Touching Money

In a blog or a marketing site, a type error is an annoyance. In code that moves money, it's a refund, a furious customer, or a financial hole. That's why everything I build that touches money is TypeScript end to end.

Money has a shape — enforce it

An amount isn't just a number. Is it kobo or naira? Is it the gross or the net? A typed money representation makes it impossible to accidentally pass a display-formatted string where an integer amount belongs. The compiler catches the mismatch before a user ever does.

State machines become safe

Order states — pending, held, released, disputed — modeled as a union type mean the compiler rejects invalid transitions and impossible states. You literally can't write code that releases a refunded order if the types forbid it.

API and webhook payloads get validated at the edge

Payment webhooks arrive as untrusted JSON. Typing the expected shape and validating at the boundary means malformed or malicious payloads fail fast and loudly, not silently three functions deep.

Refactoring stays safe as the product grows

Fintech code accumulates rules — fees, commissions, edge cases. When you need to change the fee logic, types tell you every place affected. Refactoring without that is how regressions slip into money code.

The cost is real but worth it

Yes, TypeScript adds friction — type definitions, occasional fights with the compiler. For money code, that friction is the point: it's the compiler doing the worrying so you don't ship the bug.

Takeaway

Type your money, your states, your payloads. For anything financial, TypeScript turns a class of expensive runtime disasters into cheap compile-time errors. That trade is always worth it.

Building something financial that needs to be correct? Let's talk.