You probably know this issue; you have just paid £10 and your friend will send you £5 for their share. Now you have an expense that is higher than your actual part of the transaction.

One solution here is to categorize the money you get from a friend in the same category as the expense. Then it will deduct your total expenses in that category. So if you spend £10 and get £5 from your friend, it will look like you only spent £5.