Field KZWI4 is not getting updated in table EKPO

I have a case where for two scheduling agreements the pricing procedure getting determined is the same, but the field KZWI4 (subtotal 4) in table EKPO is getting updated for one SA and not for the other. The only difference in the two SAs are the tax codes. Do tax codes have any bearing on the field KZWI4 getting updated in table EKPO?

Regards,

Pratima.