GST billing for small shops: what your bill must actually contain

This is a general explainer, not tax advice. GST rules change and your situation may have specifics — confirm with your accountant before making a decision based on it.

Tax invoice or bill of supply?

If you are registered under normal GST, you issue a tax invoice and you show the tax. If you are under the composition scheme, you issue a bill of supply, you do not collect GST separately, and the document must say so.

Getting this wrong in either direction is a problem: a composition dealer showing a tax breakup is claiming to collect tax they are not entitled to collect.

What a retail tax invoice needs to show

• Your shop name, address and GSTIN
• An invoice number from an unbroken series for the financial year
• The date
• The customer name and GSTIN, when the customer is registered
• Description of each item with its HSN code
• Quantity, unit and taxable value per line
• The GST rate and amount, split into CGST and SGST for a sale within Kerala
• The total, and the round-off if you apply one

For small-value counter sales to unregistered customers there is relief on some of this, but the safest habit is to have the software print a complete invoice every time. It costs nothing extra and removes the judgement call from whoever is billing.

The mistakes that cause real trouble

A broken invoice series

Numbers must be continuous within the financial year. Software that lets a counter skip numbers, or two counters that issue the same number, creates a reconciliation problem you will discover months later.

Wrong or missing HSN

The HSN summary is part of your return. If the code sits on the product record and gets stamped on every line automatically, this is a non-issue. If it is typed per bill, it will be wrong.

Returns handled by deleting the bill

A sales return is a credit note against the original invoice, not a deletion. Deleting the bill breaks the series and hides the transaction from the return.

Rate changes applied retrospectively

When a GST rate changes, bills issued before the change keep the old rate. Software that stores the rate only on the product — rather than stamping it onto the bill line at the time of sale — will silently rewrite your history.

What to have ready at month-end

1. 1Rate-wise outward supply summary for GSTR-1
2. 2B2B invoices listed party-wise with GSTINs
3. 3B2C consolidated by rate
4. 4HSN-wise summary with quantity and taxable value
5. 5Credit notes issued during the period
6. 6Purchase register for input credit matching

If your billing software cannot produce those six things without manual work, the software is producing your GST problem, not solving it.