GST Verification API for India: GSTIN lookup examples

Working code to verify an Indian GST number (GSTIN) with the gstinapi.in REST API: legal name, trade name, Active or Cancelled status, taxpayer type, registration date and address, live from the GST network.

Examples in Python, Node.js, PHP, Java, Go, C# and curl, plus an offline GSTIN check-digit validator in each language.

1. Get a free API key

Sign up at gstinapi.in/register and create a key on the API keys page. Every account gets up to 100 free lookups, and the credits never expire. No credit card.

Replace gak_your_key_here in the examples with your key (better: read it from an environment variable).

Free sandbox: 00AAAAA0000A1ZT returns a fixed test record with any valid key and never uses a credit, so you can build the whole integration for free.

2. The call

GET https://gstinapi.in/v1/gstin/{gstin}
x-api-key: <your key>

Response (200):

{
  "success": true,
  "gstin": "33AAACC1206D1ZN",
  "data": {
    "legal_name": "CENTRAL WAREHOUSING CORPORATION",
    "trade_name": "CENTRAL WAREHOUSING CORPORATION",
    "status": "Active",
    "taxpayer_type": "Regular",
    "registration_date": "2017-07-01",
    "address": "No.4, North Avenue, Saidapet, Chennai"
  },
  "credits_remaining": 487,
  "free_remaining": 97,
  "response_ms": 312
}

The record is under data. Status codes: 400 bad format (not charged), 401 bad key, 402 out of credits, 404 not registered (not charged), 429 rate limit, 502 GST network unavailable (retry with backoff).

3. Run an example

Language	Lookup	Offline check-digit validator
Python	python python/with_package.py (pip install gstinapi) or python python/with_requests.py	python python/gstin_checksum.py
Node.js	node nodejs/with-package.mjs (npm install gstinapi) or node nodejs/with-fetch.mjs	node nodejs/gstin-checksum.mjs
PHP	php php/lookup.php	php php/gstin_checksum.php
Java 11+	java java/GstinLookup.java	java java/GstinChecksum.java
Go	cd go/lookup && go run .	cd go/checksum && go run .
C# (.NET 8)	cd csharp/Lookup && dotnet run	cd csharp/Checksum && dotnet run
curl	sh curl/lookup.sh

python/with_retries.py and nodejs/with-retries.mjs show the retry policy: retry only 429 and 502, with backoff.

More endpoints (same key)

• Return filing history (GSTR-1, GSTR-3B): GET /v1/gstin/{gstin}/returns
• Monthly or quarterly (QRMP) filer: GET /v1/gstin/{gstin}/filing-preference
• Everything in one call: GET /v1/gstin/{gstin}/complete
• All GSTINs under a PAN: GET /v1/pan/{pan}/gstins
• HSN / SAC code lookup: GET /v1/hsn/{code}
• E-way bill and e-invoice generation

Full reference: API docs · OpenAPI spec · Postman collection · Language guides

Official libraries and tools

• Node.js: gstinapi on npm
• Python: gstinapi on PyPI
• No code: Free GST number search and bulk Excel check

License

MIT. Results come from the GST network at the time of the call; verify independently before decisions with legal or tax consequences. gstinapi.in is not affiliated with the Government of India.