HiI am a sole trader. I categorise my room rental under rental/utilities. Can anyone explain why this is appearing as a disallowed tax expense. it is allowed

The Detail type of the expense account you are using (Rent/Utilities) may relate to a portion of any bill that pertains to personal or non-business use.

When you set up an account, QuickBooks uses the Detail type to automatically allocate your spending to a specific line on your Self Assessment (SA103) form. If you selected a detail type indicating non-wholly business use, QuickBooks will assume that the expense is for personal use, rendering it a disallowable tax expense.

To ensure you're using the correct account detail type for the rent expense, click on the Gear icon > Chart of accounts. Locate the Rent/Utilities account and check the detail type listed in the Detail Type column. If it's incorrect, edit it by clicking the dropdown > Edit, and then choose Utilities or another detail type that reflects expenses incurred exclusively for business purposes.

After making the changes, be sure to click Save. This will ensure that the expenses recorded under Rent/Utilities will be recognized as allowable business expenses.

If you have any additional questions, please feel free to revisit this thread.