Fixing pair of invoices with negative/positive off-setting balances?

Well, my Subject line may be a bit confusing!  I have two invoices for a client.  One shows a balance due of $631.15.  The other shows a balance of negative $631.15.  Clearly, one offsets the other --- but I have no idea how to tell TM that both invoices are paid.  Hopefully, I don't have to undo all the subsequent invoices to get this fixed.  Any ideas?

-Micah

I would start by checking all the payments on the client to make sure each payment was properly applied. If that doesn't help, let us know and we can make some other suggestions.