Why does a client's balance in QuickBooks not match what's in PetPocketbook?

Prior balance

If you did not import data across all time and instead only activity beginning from a specific date in PetPocketbook (aka your "import start date"), there may be billing history not imported that's creating this discrepancy. Perhaps there's credit from a payment collected, or there's a bill that was sent prior to your import start date that's being paid off by a payment that occurred after your import start date. If that's the case, you may want to manually create certain records from prior to your import start date to correct your client's balance.

How QuickBooks accounts for credit

Unlike PetPocketbook, QuickBooks does not by default automatically apply credit to your client's balance when you've added a discount adjustment to their bill that results in a net credit balance. When a PetPocketbook invoice with a credit balance is imported, QuickBooks creates a "credit memo" instead of an invoice to account for the credit. QuickBooks leaves this credit memo "unapplied," which means that invoices in PetPocketbook that were partially or in its entirety paid by this credit balance will appear as outstanding in your QuickBooks account. Because QuickBooks only looks at open overdue invoices for a client's balance without regard for these credit memos, the total balance for a client who's had a credit balance at any point in their billing history with you will be different in QuickBooks vs. what you see as their outstanding balance in PetPocketbook. The screenshot below shows an example of an imported invoice with an outstanding balance that should have been paid by the unapplied credit memo that QuickBooks created to account for a prior credit balance.

To match what you see in QuickBooks to the correct balance in PetPocketbook, you'll need to link the unapplied credit memos to the open overdue invoices that they were used on by tapping "receive payment" on the outstanding invoice and then selecting the appropriate credit memo that should be applied to that invoice. Learn more about applying credit memos to an invoice in QuickBooks.