They all look the same.

Biz GST Pro Five documents A customer, a list of items, a total. That is where the similarity ends — and sending the wrong one is easy to do and annoying to unwind. bizgstpro.com

Before anything is agreed.

Quotation A price you are offering. It commits nobody and creates no receivable. Its only job is to let the customer say yes or no.

Looks like an invoice. Is not one.

Proforma A statement of what the invoice will say, usually sent so the customer can arrange payment or approval first. It is not a tax document and should not be treated as one by either side.

This is the event.

Tax invoice It records a supply that actually happened and it carries the tax. Everything before it was preparation. Your books and your customer's input credit both rest on this one.

Not a delete button.

Credit note A return, a shortfall, an agreed discount after the fact. The original invoice stays and the credit note records the adjustment against it — which is exactly what makes the history readable a year later.

Editing an invoice you already issued.

The costly mistake It feels tidier and it destroys the trail: your copy and the customer's copy now disagree, and nobody can say what changed or when. A credit note is longer to explain and shorter to live with.

Start free, no card.

Biz GST Pro GST invoicing, customer ledgers, stock and reports — built for Indian businesses. bizgstpro.com Read the full guide