can you update an invoice with a cash payment?

Click on the three dots next to the payment (on the right side) and click “mark as paid”. It will give you an option to log CASH.

Thank you I found it. I should have also asked if there's a way to indicate a partial payment?  

@Bourne-Voyage , if you know ahead of time that they’re going to pay in installments, you can adjust the payment schedule to reflect that.

If you don’t, then I’d go in and edit the invoice, edit the payment schedule to reflect today’s payment, leaving the remainder due on the due date. Then you can save (Honeybook will require you to send them an email with the update), and mark the cash payment as paid.