Hey looking for help. I receive money in from customers in order to pay off an invoice. How do I mark their transactions?

You got me here to help you out with marking your customer's invoice as paid, emmajanepovey. 

The process is super quick and easy. You'll just have to click the Mark as paid option in the Action column. 

I've attached screenshots as your visual reference:

That's it! you're now able to mark your customer's invoice as paid in QuickBooks Self-Employed.

I've also added this link about invoicing feature in QBSE: Easy invoicing in QBSE

The Community is always here if you have other questions. Keep posting!