Tax is the cost most often left out of a pricing decision and most likely to arrive as an unpleasant surprise. These calculators produce planning estimates so the money is set aside before it is spent.
Which one you want
VAT handles adding and removing value-added tax at any rate, including working backwards from a gross figure — the calculation that trips people up most, since removing 20% VAT means dividing by 1.2, not subtracting 20%. Freelance Tax estimates the self-employment liability independents should be reserving from each invoice. Payroll Tax covers the employer side, which is the part that surprises first-time hirers.
What the numbers mean
The single most useful habit these support is reserving tax on receipt rather than at filing. A freelancer who moves 25–30% of every payment into a separate account on the day it arrives never faces a quarterly bill they cannot pay. Rates, thresholds and allowances change between jurisdictions and between tax years, and these calculators are planning tools rather than filing tools — check the current figures with your tax authority or an accountant before submitting anything.