Because they live in spreadsheets. The estimate is emailed, the job changes twice, and the invoice is built from memory of a document nobody can now find.
An estimate is a priced, non-binding view of what a job would cost, built from catalogue lines and kept on the customer record rather than in a file.
Lines come from the catalogue at the current rate. On acceptance the estimate converts to a quotation or straight to a sales order, carrying its lines and rates forward instead of being retyped.
A client asks roughly what a migration would cost. You estimate against indicative lines, mark them provisional, and convert only the lines that survive scoping — the rest expire with the estimate.
It does not commit stock or capacity. Nothing is reserved until it becomes an order, so two estimates can cheerfully promise the same week.
An accepted estimate becomes a quotation or a sales order, and from there a challan and an invoice. Flow shows it on the opportunity, so pipeline value is the estimate rather than a guess.
An estimate is indicative and expires; a quotation is a firm offer with fixed terms. Both convert to an order.
Yes. Each revision is numbered and kept, so you can see what changed between v1 and v3.
No. Nothing posts until an invoice is issued.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.