Set up GST correctly

Getting GST right comes down to one thing: WHMCS must charge IGST on inter-state sales and CGST + SGST on sales within your own state. GST Manager sets this up for you once you tell it who you are — your GSTIN (your 15-character GST registration number) and your registered state. This guide walks you through it and shows you how to confirm it works.

Why the client's state matters

GST splits by geography. When your client is in another Indian state, you charge a single IGST (Integrated GST). When your client is in your own state, you charge two halves — CGST (central) plus SGST (state). GST Manager generates both rule sets so WHMCS picks the correct one automatically from each client's state.

1. Enter your GSTIN and registered state

You can do this two ways:

• During first-run setup — on Step 3, GSTIN & Tax Rules of the Setup Wizard, enter your 15-character GSTIN and pick your registered state. This is the only mandatory step in the wizard; an invalid GSTIN is flagged in red and you can't continue until it's valid.
• Any time afterwards — go to Addons → GST Manager → System Setup → Tax & GST, fill in the Tax Type and your GSTIN, and save.

Addons → GST Manager → System Setup → Tax & GST

2. Generate the IGST / CGST / SGST rules

From the same Tax & GST screen (or wizard Step 3), generate the tax rules. GST Manager creates:

• IGST 18% — applied at the country level (India), for inter-state clients.
• CGST 9% + SGST 9% — applied for clients in your registered state.

One-Click System Setup

In a hurry? System Setup offers a One-Click System Setup that configures invoicing, your GSTIN and the tax rules together in a single step — handy if you skipped parts of the wizard.

3. Verify the WHMCS tax configuration

The rules only fire correctly when each client's state is recorded, because the client's state is what drives CGST/SGST vs IGST. To confirm everything is wired up:

1. Open a test invoice for a client in your own state — you should see CGST 9% and SGST 9% line items.
2. Open an invoice for a client in a different Indian state — you should see a single IGST 18% line item.
3. If a client shows no tax, check that their state is set on their profile and that the WHMCS prerequisites (per-line-item tax, taxable item types) are enabled — the wizard's WHMCS Prerequisites step fixes these with one button.

Client state is the switch

If a client's state is blank or wrong, WHMCS can't tell inter-state from intra-state and may apply the wrong tax (or none). The GST Compliance Health widget on your dashboard flags zero-tax domestic invoices so you can catch these quickly.

Related pages

• Setup wizard — the guided 7-step first run
• Settings reference — every System Setup field explained
• GST Manager overview