How to add tax or extract it from an inclusive price

Identify the amount you have

A net amount excludes tax. A gross amount includes tax. The calculator offers one mode for adding a flat tax rate to net and another for extracting the included tax from gross. Choosing the wrong mode can apply tax twice or remove it incorrectly.

Use the rate applicable to your transaction. The examples here use a hypothetical 10% rate to show arithmetic, not to establish a rate, exemption or obligation for any country. Confirm those details with the relevant tax authority or your adviser before preparing an invoice or return.

Example: add 10% to a net amount of 100

Tax = 100 × 10 ÷ 100 = 10. Gross = 100 + 10 = 110. In Add tax mode, enter amount 100 and rate 10. The results show Net amount 100, Tax amount 10 and Gross amount 110.

To reverse that calculation, choose Extract tax from a gross amount and enter 110 at rate 10. Net = 110 ÷ 1.10 = 100, and tax = 110 − 100 = 10. Subtracting 10% of the gross would instead give 99, which is incorrect because the original tax was based on net.

Use the calculator

1. Check whether the price already includes tax. Look at the invoice or quote rather than guessing.
2. Select Add tax to a net amount or Extract tax from a gross amount.
3. Enter the amount and your percentage rate. Enter 10 for 10%, not 0.10.
4. Choose Calculate and compare all three amounts. Net plus tax should equal gross before display rounding.
5. Use the same currency throughout and check the required rounding convention for your invoice or accounting system.

Where this calculation stops

The tool applies one flat rate to one amount. It does not combine several taxes, determine eligibility, model exemptions or apply jurisdiction-specific invoice rounding. For items with different rates, calculate each applicable amount separately according to the rules you need to follow.

Results are rounded to two decimal places for display. Rounding tax for each line can differ from rounding a total at the end, particularly for small amounts. Match your required method instead of assuming that a display total is ready for a tax filing.