This article explains the use of the Income Tax sheet within the Basic Sole Trader package.
The Income Tax sheet in the Basic Sole Trader package just focuses on the business side of things so it's is only an indication of your bill.
If you have more complex circumstances you could just ignore it and leave a pessimistic allowance in your drawings until file your return.
When filing your tax return the DIY Accounting package will help you complete the Self Employment supplement, then you'll get the exact amount of tax to pay HMRC after completing other sections for personal circumstances and PAYE income.
It is possible to adjust the Income Tax calculation:
These steps permanently alter the formula, take a backup if you are unsure if you want to make the changes.