Hi!

I run an auto glass business and our customer is a corporate body shop.  I invoiced them for a job in May, and got paid the first time in June. Everything is fine at this point.

I was paid a second time in July.  Oops. 

In August, they deducted the amount twice, then paid the amount a third time.  If you're keeping score, we're even from an income perspective, but it's a mess in my quickbooks.  I have "unapplied credits" and I don't know how to reconcile this.

This is an ongoing issue and this was just one example.  I have tried talking to the customer, but she insists this is "how they do it" and is not going to change their way of doing things, so I need to adapt.  What do I need to do to adapt?  This is otherwise a good account to have since they reliably pay on time.

Do I need to write a journal entry each time this happens?  Sales receipts and returns?