Thanks for your post,
We've got a guide here which covers which transactions are allowable and disallowable for each category in line with HMRC's Self-Assessment deduction categories. Please compare this to your Tax Summary report where you'll see the total allowable and disallowable amount showing against each, and you can click into the figures from here to see which specific transactions are posting against this.
If you feel this is calculating incorrectly please get back to us below so we can take a closer look. 🧐
Thanks for sharing a screenshot with us, @nicolaboote-hotm.
I got some steps we can perform to isolate this issue. I suggest clearing your QuickBooks Self-Employed mobile app data. Let me guide you how.
For more insights, you can refer to this article (this also apply to QBSE Mobile App): Troubleshooting Quick-Start Guide for the QuickBooks Online app.
Moreover, I’m adding this link that you can use for guidance in categorising transactions in your QBSE account.
You can always tag me in your reply if you have other concerns or questions managing your transactions. It’s always my pleasure to help and keep you in working order. Have a good one!