How Mallow reconciles with existing QuickBooks invoices
When a Mallow invoice shares the same invoice number as a record already in QuickBooks Online, Mallow updates the existing QuickBooks invoice rather than creating a duplicate. When the customer pays through Mallow, the integration creates a linked QuickBooks Payment record against that open invoice.
How Mallow matches an invoice
Mallow matches the invoice number and customer from your portal to find the corresponding QuickBooks record.
If Mallow finds a single matching QuickBooks invoice for the same invoice number and customer, it performs a sparse update on the existing record. It does not create a duplicate invoice.
What happens when the customer pays
When a payment is received in Mallow:
Open invoice: The integration creates a QuickBooks Payment record and links it to the matched open invoice.
Already paid invoice: If the QuickBooks invoice balance is already zero or less, the payment sync stops and does not create another payment record.
What happens when there is no match
If no QuickBooks invoice exists with the same invoice number, Mallow creates a new invoice record in QuickBooks.
Duplicate invoice numbers
If multiple QuickBooks invoices share the same invoice number and none matches the mapped customer, Mallow raises an error. Resolve the duplicate invoice number in QuickBooks before retrying the sync.
Make sure your customer mapping in Mallow is correct before syncing. An unmapped customer shows as No QuickBooks customer mapping in the reconciliation view.
For setup instructions, see Connect Mallow and QBO. For general sync behavior, see What does the Mallow x QBO integration do?