---
title: "Naming Series as Per GST Rules"
space: "ERPNext"
url: "https://docs.frappe.io/erpnext/naming-series-as-per-gst-rules"
updated: "2026-07-31"
---

Rule 46 (b) of the CGST **Rules** 2017 specifies that the tax **invoice** issued by a registered person should have a consecutive serial **number**, not exceeding sixteen characters, in one or multiple series, containing alphabets or numerals or special characters – hyphen or dash and slash symbolized as “-” and “/” respectively

  


This validation will come into effect in ERPNext from the new fiscal year i.e FY 2021-22. If you encounter an error similar to one shown in the screenshot below, follow the below steps to resolve the issue and add a new naming series for Sales and Purchase Invoices

  


![](/files/Nr1n53j.png)

  


Step 1: Go to "Naming Series" doctype and select transaction as "Sales Invoice"

  


![](/files/1KrOqdx.png)

  


Step 2: Add a new naming series having maximum upto 16 characters. For eg INV-.YYYY.-.#####. Add this as the first option and don't check "User must always select" inorder to make this as the defaut naming series

  


![](/files/hrHZ0Rv.png)