how do I claim potential deductions for my business mileage on my self assessment? do I use the P87 form or add to my self assessment? if the later, what category does it come under? owed £5.4k up to know, 13,447 business miles done?

Hi MDS54, thanks for joining the Community -  QuickBooks Self-Employed offers two ways to track your business mileage deductions. You can either enter your trips and automatically track your mileage using the simplified expenses method (pence/mile), or you can use the actual expenses method to calculate and enter your vehicle costs (on the transactions tab, categorised these as Car/van expenses). You can see the differences between the two explained here. 🙂