Understand and navigate the access model for retrieving GSTR-2B or verifying GSTIN taxpayer details programmatically - GSTN returns and taxpayer APIs are GSP-gated, not self-serve.

Documented steps

1. Establish the access path first: GSTN's Returns and taxpayer-search APIs are exposed only through a licensed GSP (GST Suvidha Provider) that holds the GSTN API licence key and issues sub-licence keys. There is no public self-serve API signup.
2. If you are building an application layer (an ASP), integrate on top of a GSP's licensed connectivity - an ASP cannot obtain its own GSTN licence.
3. The taxpayer authenticates once via an OTP sent to the GST-registered mobile number or email. After that the GSP is authorised to act on the taxpayer's behalf without repeated OTPs for the session.
4. Successful authentication issues a token plus a Session Key with a bounded validity window; both are required on all subsequent Returns-module calls.
5. Call Returns-module APIs through the GSP. These cover invoice upload/modify, accept/reject/modify of counterparty invoices, auto-populated data retrieval, and generation and filing of the GSTR series.
6. GSTR-2B (auto-drafted ITC statement) falls under the auto-populated-data category. It is a monthly point-in-time snapshot generated by GSTN, so you are fetching the latest generated statement rather than running a live query.
7. Taxpayer search (Tax Payer or Tax Consultant search) is likewise exposed only as a GSP-mediated API.
8. Do not attempt to script the public www.gst.gov.in 'Search Taxpayer by GSTIN/UIN' page - per GSTN's own user manual it is a portal UI feature only, not a programmatic API.
9. Build re-authentication logic for long-running batch jobs, since session tokens expire within the GSP framework's bounded window.
10. Official docs: https://www.gstn.org.in/assets/mainDashboard/Pdf/GSP_Implementation_Framework_V_3.0.pdf | https://tutorial.gst.gov.in/userguide/taxpayersdashboard/Search_Taxpayer_manual.htm