>The fields have to have the same type

Ok, so the problem field appears to be the currency one.

select 00000000.0000 As pmtAmount, ;
	from invoice ;
	union ;
	select payment.yAmount + yTax As pmtAmount, ; && yAmount and yTax are both currency fields.
	from payment

What should the template be? or do I need to trans the payment.yAmount + yTax As pmtAmount?