Every tool here does its arithmetic correctly. That is the easy part, and it is not where things go wrong.
What a calculator cannot do is know your situation. It does not know whether the expense you counted is deductible, whether your free zone licence category actually qualifies for the 0% rate, whether your contract is unlimited or fixed-term, or whether an election you assumed was available has already been used up. It applies a formula to the numbers you type. If the numbers going in reflect an assumption that turns out to be wrong, the answer coming out is wrong with complete confidence.
Three places where that gap matters most in practice:
- Corporate tax. The calculator works from taxable income. Getting from accounting profit to taxable income is where the real work sits — disallowable expenditure, related-party pricing, provisions that do not yet qualify. Most companies have never done that exercise properly, as we set out in the errors we see most.
- The free zone 0% rate. Selecting "yes" shows zero tax. Whether you are actually entitled to it depends on six cumulative conditions tested every period, and failing one loses the status for that period and subsequent ones. Read the QFZP guide before you plan around it.
- Gratuity and leave. The formulas model the standard position. Specific contracts, unpaid leave, limited-term arrangements and negotiated settlements all change the outcome.
Use these to get a sense of scale, to sanity-check something you have been quoted, or to work through a problem for yourself. When the number is going into a decision that matters, have someone look at the assumptions underneath it. That conversation is free here and it usually takes twenty minutes.