Invoices, receipts, and estimates serve three different moments in a transaction. Mixing them up creates confusion for clients and headaches for your bookkeeping.
Invoice: a request for payment
You send an invoice after you complete the work or deliver the product. It lists what the client owes, item by item, and includes a due date. You record the invoice as an account receivable on your books. Until the client pays, the invoice stays open. After the client pays, you close it. An unpaid invoice means the client still owes you money. A paid invoice becomes a record for your end-of-year tax filing.
Receipt: proof that payment happened
You issue a receipt after the client pays you. It confirms the amount received, the date of payment, and the payment method. Issue the receipt and the transaction is done. The client keeps it for their own expense records. You keep a copy for your accounts. Receipts matter most at tax time. If the tax authority audits you, receipts prove your reported income and expenses. Without a receipt trail, you are relying on bank statements alone.
Estimate: a price preview before work begins
You send an estimate before starting any work. It gives the client a ballpark figure so they can approve the budget. An estimate is not a binding commitment. The final invoice may differ from the estimate if the scope changes. Label estimates clearly as "Estimate" so the client does not mistake it for a bill. A quote is a more formal version of an estimate. A quote carries legal weight and locks in the price. Estimates remain flexible.
When to use each document
Send an estimate at the start of a project, before the contract is signed. Send an invoice when the work is done and you want payment. Send a receipt after payment arrives. The order matters: estimate before work, invoice after work, receipt after payment.
The document chain in practice
Example: a web designer meets a new client. They send an estimate for $3,000 covering homepage, three inner pages, and contact form. The client approves. Work begins. Two weeks later, the site launches. The designer sends an invoice for $3,000, due in 7 days. The client pays via bank transfer. The designer sends a receipt confirming $3,000 received on that date. The job is done. The paper trail is complete.
Why the distinction matters for your business
Use estimates to contain scope creep. When the client asks for extra pages, reference the original estimate and send a revised one. Send invoices fast: the sooner they go out, the sooner you get paid. Save every receipt you issue and every receipt you receive. Your accountant needs both at tax time.
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