Sales Tax Error Message in US Version 4 SP2

Hi Forum, I am getting an error message when trying to post a sales Order which has me confused. The Sales Order has 2 Sales Lines, 1 is the item (1120) for $100.00 and the other is a G/L Code (8628) also for $100.00. when I try and post it I get the message…

“The Sales Tax Amount for the Dallas, TX Tax Area Code and the Materials Tax Group Code is incorrect. The Calculated tax amount is -80 but was supposed to be -48.5.”

If I create an Order for just the item, it posts and calculates the Sales Tax correctly, if I create an order for just the GL Code it posts and calculates Sales Tax correctly BUT… put them both in the same order I get the error message. Boy am I confused. Can anyone shed any light on this…Paul

Solved. For some strange reason the Tax Group Code was upsetting it.