Practical guide
Estimate to invoice
An estimate tells a prospective customer what work is likely to cost; an invoice bills them for it. The moment an estimate is accepted, it becomes the natural starting point for the invoice: same parties, same line items, same currency. Converting instead of retyping saves time, but the real payoff is accuracy - the price the customer approved is exactly the price they are billed, with no transcription errors between the two documents.
Who needs this workflow
- Freelancers quoting project work (design, writing, development) where the client approves a scoped estimate before work begins.
- Contractors and trades whose estimates list labor and materials, and whose invoices must match the approved figures line for line.
- Small ops teams that need an audit trail from "what we proposed" to "what we billed" - the conversion keeps both documents linked.
Step-by-step: converting an accepted estimate
- Confirm the estimate is still current. Check the "valid until" date and that the scope has not changed since acceptance. If prices or scope moved, revise the estimate first and get it re-approved - do not silently adjust figures at the invoice stage.
- Open the estimate and click Convert → Invoice. The line items, parties, currency, and locale carry over. The estimate's "valid until" date is dropped - the invoice has its own issue and due dates.
- Review the import modal. It enumerates copied, changed, and omitted fields so you can see exactly what the invoice inherited before confirming.
- Set the invoice-specific fields. The ones that matter:
- Invoice number - a new number from your invoice sequence. The estimate number is retired, not reused; the invoice records where it came from.
- Issue date and due date - the invoice's own dates. The due date drives payment terms (e.g. issue date + 14 or 30 days), so set it deliberately.
- Deposit already collected - if you took a deposit against the estimate, show it on the invoice and bill only the balance (see the example below).
- Payment details - bank details or accepted methods, which estimates usually omit.
- Confirm and save. The estimate stays in your saved drafts; you can keep the estimate and the invoice side by side.
Common mistakes
- Editing prices during conversion. If the final cost differs from the estimate, tell the customer before invoicing. A surprise on the invoice is how disputes start.
- Forgetting the deposit. Invoicing the full total after a deposit was paid is the fastest way to a confused customer and a delayed payment.
- Reusing the estimate number as the invoice number. They are different document series; mixing them breaks both sequences.
Worked example: estimate, discount, tax, deposit, balance
A developer's estimate EST-2041 is accepted with a 5% new-client discount, a 6% tax rate, and a 50% deposit payable up front.
| Line | Amount | Arithmetic |
|---|---|---|
| Design, 12 h × $85.00 | $1,020.00 | 12 × 85.00 |
| Development, 20 h × $95.00 | $1,900.00 | 20 × 95.00 |
| Subtotal | $2,920.00 | 1,020.00 + 1,900.00 |
| Discount (5%) | −$146.00 | 2,920.00 × 0.05 |
| Taxable amount | $2,774.00 | 2,920.00 − 146.00 |
| Tax (6%) | $166.44 | 2,774.00 × 0.06 |
| Total | $2,940.44 | 2,774.00 + 166.44 |
| Deposit received (50%) | −$1,470.22 | 2,940.44 × 0.50 |
| Balance due on invoice | $1,470.22 | 2,940.44 − 1,470.22 |
The invoice converted from EST-2041 shows the same line items and totals, plus the deposit already received and the balance due. The customer can trace every figure back to what they approved.
Estimate vs adjacent documents
- Estimate vs quote - largely a regional naming difference for the same pre-sale document; see theestimate vs quote comparison.
- Invoice vs proforma invoice - a proforma looks like an invoice but is issued before supply, often to trigger an advance payment; see theinvoice vs proforma comparison.
- Estimate vs work order - an accepted estimate can also become a work order that authorizes the job internally before any billing happens.
Frequently asked questions
Does the estimate number carry over to the invoice?
No. The invoice gets a new number from your invoice sequence, and the estimate number is recorded as the invoice's source reference. That keeps both numbering series clean while preserving the link.
What if the scope changed after the estimate was accepted?
Issue a revised estimate (or a change order) and get it approved before invoicing. Invoicing an amount the customer never saw is the most common cause of payment disputes for small businesses.
Can I invoice more than the estimated amount?
Only with the customer's prior agreement. An estimate is not usually a fixed-price contract, but billing above it without warning damages trust - agree on overruns in writing first, ideally as a revised estimate.
Can I invoice part of an estimate?
Yes. Convert the estimate, then remove or reduce lines to bill a milestone, noting on the invoice which portion of the estimate it covers. Repeat for later milestones, each on its own invoice number.
Should I delete the estimate after converting it?
No - keep it. The estimate is your record of what was approved. The conversion preserves the estimate in your drafts precisely so the pair can be reviewed together later.
What happens to the "valid until" date?
It is dropped. Validity windows belong to pre-sale documents; the invoice replaces it with an issue date and a due date.
Doing this in Formnivo
Build the estimate in the estimate generator, then use Convert → Invoice to open theinvoice generator with the approved items carried over. The new invoice carries a provenance pointer back to the estimate - its id, number, and schema version - and the estimate itself is preserved in your saved drafts. Everything runs locally in your browser: no account and no document upload. Data stays browser-local unless you export or share it yourself.