Incorrect Due Date on imported Puchase Invoices

SOLVED

Hi All, 

We are using .IMP files to import Purchase Invoices. There is no such field Due Date in the file format, so we do not send it. 

Sage automatically sets this date to Entry Date even if the customer is configured for a 21-day delay. 

The manual entry of invoice is ok, the due date is correctly calculated. 

Is there a way to configure the due date calculation for the file importing process? 

Thanks