Open Source

The law belongs to everyone. So does the arithmetic.

The calculation engine behind our calculators is published as vatkenya — a zero-dependency, fully typed MIT package covering VAT arithmetic, KRA penalties, eTIMS minimums and filing deadlines. Use it in your own products, audit every line, or file an issue when the law changes.

Install

npm install vatkenya

Use

import { addVat, removeVat, vatPenalty, etimsPenalty, vatDeadline } from "vatkenya"

addVat(1_000_000)          // { net: 1000000, vat: 160000, gross: 1160000 }
removeVat(1_160_000)       // { net: 1000000, vat: 160000, gross: 1160000 }
vatPenalty(137_931, 12)    // full penalty + compounding interest breakdown
etimsPenalty(50_000)       // 100000 — Finance Act 2026 company minimum
vatDeadline("2026-09-05")  // { periodStart, periodEnd, dueDate: '2026-10-20' }

Why open-source it

Correct arithmetic is a public good

Every Kenyan fintech, ERP and accounting package eventually re-implements the same spreadsheets — and gets the details wrong: flat versus compounding interest, the KES 10,000 filing floor, the 2026 eTIMS minimums. Publishing the version we run in production raises the floor for everyone, and makes our own work auditable: if our calculators are wrong, thousands of developers can prove it.

The package exports LAW_VERSION — the date the encoded law was last verified. We re-verify after every Finance Act, the same process documented in our editorial policy.

GitHub repository

Read the source, file issues, or open a pull request against the Finance Act season updates.

npm package

npm install vatkenya — zero dependencies, ESM + types, works in every modern runtime.