How EKPO-NAVNW( Non-deductible input tax) getting calculated?

Hi,

I would like to know how EKPO-NAVNW ( Non-deductible input tax) is getting calculated?

Since in EKPO table for NAVNW, value is 0.00 but in ME23n when I checked,

In Invoice tab - > Taxes -> tax is  13.00

   Conditions  tab -> Condition type NAVS - Non-Deductible Tax - Amount is 13.00.

But how it is calcualted and updated as 0.00 for NAVNW field in EKPO.

any different field for NAVNW in ME23n exist ? Please let me know.

Thanks & Regards,

Priya