Once a tax invoice is issued, you do not edit it. If the sale changes afterwards, GST expects a separate document that adjusts it: a credit note to reduce what was charged, or a debit note to increase it.
When you issue a credit note
You issue a credit note to the buyer when:
- Goods are returned, wholly or partly.
- The invoice overstated the taxable value or the tax.
- Goods or services were deficient and the buyer is not paying for all of it.
It reduces your output tax for the period in which you declare it.
When you issue a debit note
A debit note goes to the buyer when the invoice understated the value or the tax — a price that should have been higher, or extra quantity supplied.
What a credit or debit note shows
Much like an invoice: your name, address and GSTIN; its own serial number and date; the buyer’s details; the original invoice’s number and date; the value and tax being adjusted; and your signature.
The deadline
A credit note must be declared in your returns no later than 30 November following the end of the financial year in which the original supply was made, or the date you file the annual return, if earlier. Miss it, and the tax you want to reduce stays charged.
Why not just cancel and re-bill?
Cancelling is for an invoice that should never have existed — a mistake caught before it went to the customer. Once the customer has it and the sale happened, a credit or debit note is the clean way to adjust it, and it keeps your invoice series intact.
In Billyng
An issued bill in Billyng never changes underneath you, and a bill can be cancelled. Billyng does not yet issue credit or debit notes — record those adjustments in your accounts until it does.
General guidance only. Confirm with the CBIC site or your tax adviser for your own case.