Invoice vs receipt vs estimate: what each document actually proves

• Estimate proves a price offered before work starts
• Invoice proves payment is owed, a request not confirmation
• Receipt proves payment was actually received, closing the transaction
• Korean tax invoice proves VAT was charged and reported

The fastest way to tell these apart is to ask what each one would hold up as evidence of, if someone questioned it later.

• Estimate (견적서) proves a price was offered before work started, valid until a stated date — not proof of agreement or payment
• Invoice (청구서) proves a payment is owed, by whom, to whom, and by when — a request, not confirmation it was paid
• Receipt (영수증) proves payment was actually received — issued after money changes hands, the only one of the four that confirms a transaction is closed
• Korean tax invoice (세금계산서) proves VAT was charged and reported to the tax authority — a statutory document, not just a business record

• Invoice comes before payment and requests it
• Receipt comes after payment and confirms it happened
• If already paid, send a receipt, not a due invoice

An invoice comes before payment and asks for it; a receipt comes after and confirms it happened. If a client has already paid you in full, don't send an invoice with a due date — send a receipt, or an invoice with the amount paid entered so the balance due shows zero. Sending an invoice for money you already received reads as either a mistake or a second request, neither of which helps the relationship.

• A 세금계산서 is issued via Hometax after a taxable transaction
• This tool's invoices and estimates are not a 세금계산서
• 간이영수증 covers small purchases under the 30,000-won threshold
• Freelancers are usually subject to 3.3% withholding, not 세금계산서

A 세금계산서 is the statutory VAT tax invoice, issued electronically through the National Tax Service's Hometax system once a taxable transaction is confirmed. None of the documents this tool generates — invoice, estimate, or statement — is a 세금계산서 or can substitute for one; a VAT-registered business that needs one must issue it separately through Hometax or accounting software.

For small, one-off purchases, a 간이영수증 (simplified receipt) is common. The widely cited threshold is 30,000 won: for a single transaction of 30,000 won or less, a business generally isn't required to hold a qualifying receipt (세금계산서, 계산서, card slip or cash receipt) to claim the expense for corporate or income tax purposes. Above that threshold, the rules get stricter, and — separately — input-VAT credit is a different question from whether an expense is deductible at all; a 간이영수증 alone typically does not support a VAT credit even under the 30,000-won expense rule. Splitting one purchase into several under-30,000-won receipts to dodge the requirement is specifically flagged in Korean tax guidance as improper.

Freelancers and individual contractors paid under a service contract in Korea are commonly subject to 3.3% withholding: the payer withholds 3.3% of the fee (3% income tax plus local surtax) and reports it, rather than the freelancer issuing a 세금계산서. If that's your situation, you typically bill with an invoice or statement and a bank account rather than a tax invoice — which is exactly the kind of document this tool's invoice and statement pages produce.

These are general practices, not a substitute for advice on your specific situation — thresholds, exceptions and reporting deadlines change, so confirm anything that affects a tax filing with a licensed tax professional (세무 전문가 확인) before you rely on it.

• Before work starts, with price unset, use an estimate
• Once work is agreed or delivered, send an invoice
• After payment is received, issue a receipt
• For VAT reporting, issue a 세금계산서 through the proper channel

Work backward from the moment you're in. Before a job starts and the price isn't locked in: an estimate. Once the work is agreed or delivered and you want to be paid: an invoice. Once you've been paid: a receipt. Once a taxable business transaction needs to be reported for VAT: a 세금계산서, issued through the proper channel, not any of the documents above.