In the Payables Transaction Entry window the system will default in the Tax Schedule ID from the Vendor's Card but it will not calculate amount in the Tax field unless the Tax Schedule ID in Vendor Card is same as Tax Schedule ID selected in Payables Setup Options window for Purchase field. We don't use Inventory module or shipping methods. Is there a way so system will auto calculate Tax based upon Tax Schedule ID brought in from Vendor's Card without having to click on blue expansion arrow beside Tax field and select Tax Detail ID in Payables Tax Entry window?

Simulation : 

1 Go to  window  Company Setup Options
Administration >> Setup >> Company >> Company >> Options
Unceklist : Use Shipping Method when selectiong Default Tax Schedule
Klik OK Button to saving this configuration

2 Go to  Company Setup Window and let the Purchase Tax Schedule field blank , if there is tax schedule deleted it
Administration >> Setup >> Company >> Company
Klik OK Button to saving this configuration

3 Go to  window Vendor Address Maintenance 
Choose VendorID and Address ID then on the field Tax Schedule choose Tax Schedule to mapping

After point 1 to 3 is DONE then create Payables Transaction Entry
Original GP cannot fill calculation Tax Schedule on Purchase Tax
View Original GP

Customization :

Purchase Tax Schedule ID = Tax Schedule ID