To do this, click Start > Configuration> Accounting > Sales Tax Regimes and from the list in the right-hand grid select the appropriate Tax Regime. Remember, you can apply a filter to find the Tax Regime you're looking for quickly. NOTE: The code for the UK Tax Regime is GB and the description is United Kingdom.
To add a new Tax Code click on the appropriate row and then on New Sales Tax Code. Enter a Code (which must be unique) and a Description, then click on New Sales Tax Rate and enter the appropriate percentage rate. You must enter a date in the Valid From column and, if you want, you can also specify a date when the rate is no longer applicable under the Valid Until column. Remember to click Save & Close.
Similarly, if you want to amend the details of an existing Tax Code, click on the appropriate row, make the required changes and click Save & Close.