For 3rd party transporter invoices - GST taxes should get defaulted along with AP invoice

My requirement:

1. For 3rd party transporter invoice GST taxes should get defaulted along with the AP invoice import a t the time of MRN creation.

for this I have attached GST tax category and assigned at supplier 3rd party registration site level under Stand alone invoice column.

After MRN creation RTP and 3rdparty concurrent requests fired normally, But if i open AP transporter invoice distributions are blank, FND debug log shows tax location and ORg are blank, unless AP distributions are saved, we can not select India tax details form

any help in this regard

Thanks

Thriveni