QuickBooks doesn’t have a dedicated “PO number” field that Breww can use. Instead, they have “Custom fields”, which you can set up with a name and whether you’d like them displayed on your sales invoices. When uploading an invoice to QuickBooks, Breww checks for a custom field called “PO number” (which QuickBooks may now create as a custom field by default), “PO reference”, or “PO no”. If a custom field with this name exists, Breww will populate it with the PO number from the invoice in Breww.
There is a thread on the QuickBooks forum as to how to manage your custom fields (here). Follow that guide to add a custom field called “PO number”, and Breww will start populating this value in QuickBooks.
If you’ve renamed this field to something else, you’ll need to rename it to “PO number” , “PO reference”, or “PO no” in order for Breww to find and use it.