How to Convert an Estimate or Quotation into an Invoice
When a customer accepts your quotation, the invoice should match it without retyping a single line. Here is what carries over, what you must check before you send it, and how the Convert button works in BillBabu.
BillBabu Team
BillBabu App Team
In short
- Convert an estimate into an invoice after the customer accepts it and when you supply the goods or finish the work.
- The party, items, quantities, rates and place of supply carry over. The invoice gets its own number and date.
- Before you send it, check the GST rates, the quantities actually delivered and any advance already paid.
- In BillBabu, the one-click Convert button is in the web app. The Android app does not have it yet.
When to convert
An estimate or quotation is an offer. The invoice is the bill for what you actually supplied. So the right time to convert is not when the customer says yes, but when you supply:
- Goods: issue the invoice at or before delivery.
- Services: issue it when the work is done, and under GST within 30 days of providing the service.
If you need money before supplying, send a proforma or an estimate marked for advance payment, and convert to the invoice later. Our guide to the difference between an estimate, a quotation and an invoice explains why.
What carries over and what changes
| Detail | On the estimate | On the invoice |
|---|---|---|
| Party (customer) | Gupta Traders | Same |
| Items, quantities, rates | As quoted | Same, unless the order changed |
| GST rate per item | As on the quote date | Must be the rate in force on the invoice date |
| Number | Estimate series (EST-…) | Next number in the invoice series (INV-…) |
| Date | Quote date | Invoice date (the day of supply) |
| Valid-until date | Yes | Not needed |
| Payment terms and due date | Optional | Add them |
The GST row matters more than it looks. A quotation from before 22 September 2025 may carry an old GST rate. If you supply now, the invoice must use the current rate. See the new GST rates.
Step by step: converting in BillBabu
The Convert button is in the BillBabu web app, so do this on a computer.
- Sign in at app.billbabu.com with the same mobile number you use in the app.
- Open Documents and go to your estimates.
- Find the accepted estimate and press Convert on its row.
- Confirm in the dialog that opens.
BillBabu then creates a new invoice with:
- the same party, items, place of supply and totals as the estimate;
- today's date and the next number in your invoice series;
- the status Draft, so you can check it before you send it.
The estimate is marked Converted and kept in your list, so you can always see which quote became which bill. An estimate can be converted only once, so you cannot create a duplicate invoice by pressing the button twice.
On the Android app: there is no Convert button yet. Create a new invoice for the same party and pick the same items from your product list; the HSN codes and GST rates fill in by themselves. Then share the invoice PDF from the app as usual.
Worked example
Verma Hardware in Jaipur (Rajasthan) quotes a contractor in Ahmedabad (Gujarat). Because the goods go to another state, the estimate carries IGST.
| Item | HSN | Qty | Rate | Taxable value |
|---|---|---|---|---|
| Cement, 50 kg bag | 2523 | 50 | ₹340 | ₹17,000 |
| Steel brackets | 7326 | 100 | ₹45 | ₹4,500 |
| Taxable value | ₹21,500 | |||
| IGST 18% | ₹3,870 | |||
| Total | ₹25,370 | |||
The contractor accepts. On delivery day, Verma Hardware presses Convert on the web app. The new draft invoice has the same two lines and the same ₹25,370 total, with that day's date and the next invoice number. They check three things: the rates are still 18%, all 50 bags and 100 brackets went on the truck, and the contractor's state is still Gujarat. Then they add payment terms ("15 days") and share the PDF.
If the contractor had taken only 40 bags, the right move is to change the quantity before sending: the invoice should show what was supplied, not what was quoted.
Checks before you send the converted invoice
- GST rate: current on the invoice date, for every item.
- Quantities: what was actually delivered or done.
- Place of supply: where the goods actually went. If the delivery state changed, the tax type may change too.
- Advance: if the customer paid an advance, record it as a payment so the balance is right.
- Payment terms: add the due date; it is not copied from the estimate.
Mistakes to avoid
- Retyping the invoice by hand from the quote. That is where wrong rates and missed lines come from.
- Invoicing before the price is final. If the customer is still negotiating, revise the estimate first.
- Making two invoices for one job by converting the same quote twice. BillBabu prevents this by allowing one conversion per estimate.
- Forgetting the estimate's terms. If your quote said "transport extra", add it to the invoice. Our quotation terms and conditions guide has lines you can use.
Invoice numbers matter too: see GST invoice number rules. The whole quote-to-bill flow is on our quotation and estimate software page.
Frequently asked questions
Can I convert an estimate to an invoice in the BillBabu mobile app?
Not yet. The Convert button is in the BillBabu web app at app.billbabu.com. In the Android app, create a new invoice for the same party and items.
What happens to the estimate after I convert it?
It stays in your list with the status Converted, so you can see which quote became which bill. It cannot be converted a second time.
Does the converted invoice get a new number?
Yes. It takes the next number in your invoice series and the current date. The estimate keeps its own number.
The customer accepted only part of my quotation. What do I do?
Change the quantities before you send the invoice, so it shows only what you actually supplied.
From accepted quote to GST invoice in one click. BillBabu is a GST billing app for Android, with a web app at app.billbabu.com. Make GST invoices and estimates, share them as PDFs and see who still owes you money. Every account starts with a 14-day free trial, and you do not need a card. Get BillBabu on Google Play or see plans and prices.
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