This tool validates NTN format only. We have no access to FBR's Active Taxpayer List (ATL) database, so it cannot tell you whether a taxpayer is actually active or inactive.
7 digits for companies/AOPs, or CNIC-based (13 digits: 00000-0000000-0) for individuals
How to Check Real Active Taxpayer List (ATL) Status
Visit iris.fbr.gov.pk and use the "Active Taxpayer (ATL) Status" search with your NTN/CNIC
Or via SMS: type your 13-digit CNIC (for individuals) or 7-digit NTN and send to 9966