Set Up India GST End-to-End

What you’ll set up

This tutorial takes an Indian SaaS seller from zero to a GST-compliant invoice. You’ll save your seller GST configuration, see how place of supply decides CGST/SGST vs IGST, connect the Invoice Registration Portal (IRP) for e-invoicing, and generate a compliant invoice for a B2B customer.

GST configuration applies to all future invoices. Finalized invoices are never modified retroactively — set this up before you start billing Indian customers.

Step 1: Save your seller GST configuration

Store your GSTIN, legal name, state code, SAC code, and default GST rate. This one call drives both invoice formatting and the CGST/SGST-vs-IGST decision.

curl -X PUT http://localhost:8080/v1/settings/gst \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "gstin": "29AABCT1332L1ZM",
    "legal_name": "Recurso Technologies Pvt Ltd",
    "trade_name": "Recurso",
    "state_code": "29",
    "sac_code": "998314",
    "gst_rate": 18.0
  }'

// The SDK has no settings wrapper yet — call the endpoint directly.
await fetch(`${BASE_URL}/v1/settings/gst`, {
  method: 'PUT',
  headers: {
    Authorization: `Bearer ${API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    gstin: '29AABCT1332L1ZM',
    legal_name: 'Recurso Technologies Pvt Ltd',
    trade_name: 'Recurso',
    state_code: '29',       // Karnataka
    sac_code: '998314',
    gst_rate: 18.0,
  }),
});

Field	Meaning
`gstin`	Your 15-character GST Identification Number. Validated against the standard pattern: 2-digit state code + 10-char PAN + entity digit + `Z` + check character.
`legal_name`	Registered legal name as per GST records.
`state_code`	Two-digit state code — the seller side of the place-of-supply comparison (e.g. `29` Karnataka, `27` Maharashtra).
`sac_code`	Services Accounting Code for your service (SaaS commonly uses `9983xx`).
`gst_rate`	Default rate as a percentage (e.g. `18.0`).

Read it back any time with GET /v1/settings/gst — note that it returns 404 until a configuration exists, which is exactly why unconfigured tenants see 0% GST.

Changing state_code later affects CGST/SGST vs IGST on all future invoices. Set it to your actual place of registration.

Step 2: Understand place of supply

GST splits by where the supply happens. Recurso derives the buyer side from the customer’s billing-address state / place_of_supply and compares it to your seller state_code:

Buyer vs seller state	Tax applied	Example at 18%
Same state (intrastate)	CGST + SGST	9% CGST (₹450) + 9% SGST (₹450)
Different state (interstate)	IGST	18% IGST (₹900)

Create the B2B customer with GSTIN and state so the invoice is correct:

curl -X POST http://localhost:8080/v1/customers \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Customer Corp Pvt Ltd",
    "email": "accounts@customer.com",
    "gstin": "27DQBPS8356J1Z1",
    "address": {
      "state": "Maharashtra",
      "country": "IN"
    }
  }'

Here the seller is in Karnataka (29) and the buyer in Maharashtra (27) — a different state — so the invoice will carry IGST at 18%. A Karnataka buyer would instead get CGST 9% + SGST 9%.

For B2B customers, always capture the buyer gstin — it puts the customer’s GSTIN on the invoice and supports their input tax credit. See GST Invoicing for the full invoice format.

Step 3: Enable e-invoicing (IRP)

If you’re under India’s e-invoicing mandate (turnover above the threshold), register your IRP credentials so B2B invoices are submitted to the government portal automatically. This is a separate endpoint from GST config.

curl -X PUT http://localhost:8080/v1/settings/irp \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "client_id": "ABCD1234EF",
    "client_secret": "sk_irp_9f8e7d6c5b4a3210",
    "username": "recurso_einv",
    "password": "s3cureP@ssw0rd",
    "gstin": "29AABCT1332L1ZM",
    "environment": "sandbox",
    "is_enabled": true
  }'

Start with environment: "sandbox" to validate credentials, then switch to production once submissions succeed. Recurso manages IRP token refresh for you; sensitive fields are masked in responses. Setting is_enabled: false pauses e-invoice generation without deleting credentials.

Ensure your IRP credentials are valid before switching to production — invalid credentials cause every e-invoice submission to fail. See E-Invoicing for retry and cancel flows.

Step 4: Generate a compliant invoice

With GST configured, invoices are generated automatically at each billing period end — no extra call. The result includes the full GST breakup. For the interstate example above:

{
  "invoice_number": "REC/2026/0002",
  "seller_gstin": "29AABCT1332L1ZM",
  "buyer_gstin": "27DQBPS8356J1Z1",
  "place_of_supply": "Maharashtra (27)",
  "lines": [{
    "description": "Pro Plan Subscription",
    "sac_code": "998314",
    "gst_rate": 18,
    "amount": 4999
  }],
  "subtotal": 4999,
  "igst_amount": 900,
  "cgst_amount": 0,
  "sgst_amount": 0,
  "total": 5899
}

When e-invoicing is enabled and the invoice is above the threshold, Recurso submits it to the IRP and attaches the IRN, acknowledgement number, and signed QR code. Check status with GET /v1/invoices/{id}/einvoice, and download the print-ready document via GET /v1/invoices/{id}/pdf.

Verify Your Setup

GST config saved

GET /v1/settings/gst returns your GSTIN and rate (not a 404).

Place of supply correct

A same-state customer’s invoice shows CGST + SGST; a different-state customer’s shows IGST.

IRP connected

Sandbox submissions succeed before you flip environment to production.

Invoice compliant

The invoice carries both GSTINs, place of supply, SAC code, and the correct tax breakup.

Next Steps

GST Invoicing

Full invoice format, SAC codes, and B2B fields

E-Invoicing

IRN, QR codes, retry and cancel

Update GST Config API

Endpoint reference

UPI & Mandates

RBI e-mandates for recurring auto-debit

Start Here

Tutorials

Billing & Monetization

Payments & Recovery

Growth & Retention

Compliance

Finance

Platform

Set Up India GST End-to-End

What you’ll set up

Step 1: Save your seller GST configuration

Step 2: Understand place of supply

Step 3: Enable e-invoicing (IRP)

Step 4: Generate a compliant invoice

Verify Your Setup

Next Steps

GST Invoicing

E-Invoicing

Update GST Config API

UPI & Mandates

​What you’ll set up

​Step 1: Save your seller GST configuration

​Step 2: Understand place of supply

​Step 3: Enable e-invoicing (IRP)

​Step 4: Generate a compliant invoice

​Verify Your Setup

​Next Steps

GST Invoicing

E-Invoicing

Update GST Config API

UPI & Mandates

What you’ll set up

Step 1: Save your seller GST configuration

Step 2: Understand place of supply

Step 3: Enable e-invoicing (IRP)

Step 4: Generate a compliant invoice

Verify Your Setup

Next Steps