I invoiced a customer for $75; they paid $100 to give me a $25 bonus. My a/r is showing <25.00> and I can't figure out how to correct this.
Only apply the $75 to the invoice. In the bank account where you deposit the payment, split the transaction with $75 staying as the invoice part and Add a $25 split line with whatever category you choose (or create). Then click the Adjust button (inside the split dialog) and correct the deposit to being $100.