GSTIN, HSN and SAC codes: what they are and where they go

What is a GSTIN?

The Goods and Services Tax Identification Number is a 15-character code issued to each GST registration. The first two digits are the state code, the next ten are the PAN of the business, then come an entity number, the letter Z and a check character.

A business with operations in several states has a separate GSTIN for each state it is registered in.

Why it matters on invoices

The supplier GSTIN and the customer GSTIN (for business customers) determine whether tax is CGST plus SGST or IGST. A wrong state code can mean the wrong tax split.

HSN vs SAC

HSN (Harmonised System of Nomenclature) codes classify goods. SAC (Services Accounting Codes) classify services. A software subscription is a service, so it uses a SAC code, usually in the 9983 group for IT and information technology services. The exact code depends on what you provide.

How many digits?

The number of digits required on invoices depends on your turnover and the type of customer. This has changed over time, so verify the current requirement.

Practical tips

• Validate GSTIN format when you capture it.
• Store one SAC code per product or plan.
• Keep customer legal names exactly as registered.
• Review codes yearly, since classifications and notifications change.

In Knock you can keep a tax code against each product so it prints on every invoice automatically.