---
url: /gst-manager-whmcs/guides/configure-gst.md
description: >-
  Enter your GSTIN and registered state, generate the IGST/CGST/SGST tax rules
  with the wizard or System Setup, and verify that WHMCS applies the right tax
  to every client.
---

# Set up GST correctly

Configure GST tax rules to charge **IGST** on inter-state sales and **CGST + SGST** within your registered state:

* **Input requirements:** 15-character statutory **GSTIN** and your registered home state.
* **Automated rule creation:** Sets up standard 18% GST tax rules in WHMCS.
* **Geographic tax splitting:** Determines tax calculation dynamically based on client location.

::: info 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

Configure your tax identity through either method:

* **Setup Wizard:** Enter your **15-character GSTIN** and select your state during **Step 3 (GSTIN & Tax Rules)**. Format errors are highlighted in red.
* **System Setup:** Go to **Addons → GST Manager → System Setup → Tax & GST**, enter the **GSTIN** and **Tax Type**, then save changes.

![Entering GSTIN and registered state](/gst-manager-whmcs/img/gst-configure-gst-tax-and-gst.png)
*Addons → GST Manager → System Setup → Tax & GST*

## 2. Generate the IGST / CGST / SGST rules

Generate the tax rules directly from the **Tax & GST** screen:

* **IGST 18%:** Configured at country level (India) for inter-state clients.
* **CGST 9% + SGST 9%:** Configured specifically for clients in your **registered state**.

::: tip 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

Validate tax rule application with test invoices:

1. **Intra-state check:** Open an invoice for a client in your registered state. Confirm **CGST 9%** and **SGST 9%** line items display.
2. **Inter-state check:** Open an invoice for a client in another Indian state. Confirm a single **IGST 18%** line item displays.
3. **Troubleshoot zero-tax:** If tax is missing, verify the client profile has a valid **State** and rerun **WHMCS Prerequisites** from the Setup Wizard.

::: warning 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](/gst-manager-whmcs/features/setup-wizard) — the guided 7-step first run
* [Settings reference](/gst-manager-whmcs/settings) — every System Setup field explained
* [GST Manager overview](/gst-manager-whmcs/)