Missing data in MIRO

Hello All,

in miro transaction, upon ticking 'calculate tax' checkbox, then clicking the SIMULATE button, a pop-up window shows. Some values are missing for the "Modvat Account" in the 'Simulate Document' window particularly in the following columns: Purchasing Document, vendor.

May I know if there's a user exit/ BAdI to populate these missing values?

thank you in advance.

Regards,

Anju