What an estimate does
An estimate describes anticipated work, quantities, rates, materials, taxes, timing, and an expected total. It helps both sides discuss scope before the work becomes a bill.
State how long the estimate remains valid and what could change the final amount. Avoid presenting an estimate as a guaranteed legal quote unless that is exactly the commitment you intend and local rules support it.
What an invoice does
An invoice records the amount being charged and tells the client how and when to pay. It normally includes a unique number, issue date, due date, line items, totals, and payment instructions.
An invoice can refer back to an accepted estimate, contract, purchase order, or completed milestone so the client's accounts team can match the bill to the approval.
When to convert an estimate
Convert the estimate when the scope is accepted and the business event that triggers billing has occurred. Review dates, quantities, rates, tax, deposits, and the final client details rather than assuming every estimate value should become final unchanged.
Keep both records
The estimate and invoice serve different purposes, so retain both. Keeping the original estimate makes it easier to explain what was proposed and what ultimately became billable.
- Estimate: proposed scope and expected price
- Invoice: payment request and final billing record
- Review the conversion before sending
- Retain the source estimate and sent invoice PDF