How do I handle a client tip?

I have a client who paid extra on an invoice “as a tip”, how do I handle it? They are a semi-regular client, do I just leave their account in credit and reduce their next invoice by that amount? That actually seems a bit rude to me, as they specifically said they paid more because I did a good job. If I keep the tip, how do I enter it in Manager?

Thanks

create a suitable account under your chart of accounts and allocate the amount to the same when entering a receipt.
for example, if the customer paid 1500 for an invoice of 1000, in the receipt create two line entries each for the invoice i.e 1000 and the tip i.e 500

Makes sense thanks!