Field help (GADFLGDUD) 

The "Control accounts" box is checked by default on the first line of the automatic journals of the purchase, sales and BP invoices. This first line is used to generate the BP tax incl. line.

If an invoice automatic journal is set up to generate the BP line elsewhere than the first line, the "Control accounts" box must be checked. Upon invoice validation, the BP tax incl. line is associated with its open items, and the invoice is then matched.