VAT Calculator — overview

Why it exists#

Search either registry for VAT calculation and you find EU packages: the biggest has four and a half million installs and covers the EU; the next has fifteen thousand a week and covers the EU and the US; one was last published in 2015.

The UAE and Saudi Arabia have had VAT since 2018, Bahrain since 2019, Oman since 2021, and Pakistan's sales tax has been in place for decades. There is nothing for any of them.

What it does differently#

• Rates with effective dates. Saudi Arabia went from 5% to 15% on 1 July 2020; Bahrain from 5% to 10% in January 2022; Pakistan from 17% to 18% in February 2023. A credit note against an older invoice must use the rate that applied then. A single number per country produces a plausible wrong answer that only surfaces in an audit.
• Extraction done properly. The tax inside a gross amount is gross × rate ÷ (1 + rate), not gross × rate — an error that overstates the tax by the rate squared and looks entirely reasonable on the invoice.
• Integer arithmetic throughout. Every amount becomes a whole number of fils, halalas or paisa on arrival. Floats drift, and a drifting invoice disagrees with the return it belongs to.
• Rounding as a decision, not an accident. Taxing each line and summing gives a different answer from taxing the total — 0.20 against 0.15 on ten lines of 0.30 — and authorities specify which. Both are available and the difference is documented.
• Treatments kept apart. Zero-rated, exempt, out-of-scope and reverse charge are all 0% and all different; two of them change what input tax you can reclaim. The breakdown reports them separately, because a return does.
• 2.0 kB, no dependencies, and the totals drop straight into a ZATCA e-invoice QR code.

Not in 1.0#

Place-of-supply rules. Whether a cross-border service is taxed where the supplier is or where the customer is, and when reverse charge applies, is a discipline rather than a lookup. treatment: 'reverse-charge' records the decision; it does not make it.

Sector rates and provincial services tax. Pakistan's provinces tax services at their own rates and the Gulf has sector-specific treatment. Encoding those would mean a table that is out of date before it ships, so the standard rates are there and everything is overridable.

Being an authority. Rates change. The table carries effective dates, rate overrides it, and the docs say to verify against the tax authority — which is the honest position for a library that cannot be updated the day a budget passes.