Work-Completion Certificate vs Invoice: When Freelancers Use Each
Two different documents that people often confuse. In short: an invoice asks to be paid, a completion certificate confirms the work was done. We break down the difference and how to use each in practice.
Many freelancers run into two terms — a “work-completion certificate (act)” and an “invoice” — and never quite figure out why both exist. In practice they get mixed up: people send the client the wrong document, or skip one entirely. This post lays out the concrete difference and when you need which.
The short answer
- An invoice is a request for payment. It is issued before payment. It says: “Here are the services/goods — please pay this amount by this date.”
- A work-completion certificate (act) is confirmation that the work is done. It is issued after the work is finished. It says: “I confirm these works were completed and the client accepted them.”
One document asks for money. The other records that the work was done. They are different.
The usual chronological flow
- You agree with the client on the work and the rate.
- You issue an invoice for payment (often a 30–50% deposit).
- The client pays — the money lands in your business bank account.
- You do the work.
- You issue a completion certificate, signing it yourself.
- The client signs the certificate on their side.
- If the deposit didn’t cover the full amount, you issue another invoice for the remainder.
- Payment again, certificate again, or one combined certificate.
Some skip the deposit: they do the work right away → issue the certificate and invoice at the same time → get paid after delivery. That’s fine, but riskier for the contractor.
What an invoice should contain
For most freelance services there are no strict legal formatting rules, so in practice an invoice should have:
- A number and issue date.
- Your details — your name/business name, tax ID, and business bank account / IBAN.
- The client’s details — name and registration/tax number.
- A description of the services — one or more lines with quantity, unit, rate, and amount.
- The total — in figures (and in words, if your local norm expects it).
- The payment due date — by when payment is expected.
- Your signature (often not required for electronic invoices).
It’s common to add a payment reference like “Payment for services per invoice #X dated DD.MM.YYYY” so the client’s bank transfer is labelled correctly.
What a completion certificate should contain
A work-completion certificate is the more serious document. In many jurisdictions it functions as a primary accounting document — proof for your books that a transaction took place.
Typical required details:
- The name of the document.
- The date it was drawn up.
- The name of the business/person issuing it.
- The content and scope of the transaction, with the unit of measure.
- The roles and names of the responsible parties.
- A handwritten or electronic signature (or other identifying data).
In practice the certificate is almost a copy of the invoice, but with:
- A different title.
- Two signatures — contractor and client.
- Often a line such as: “The parties have no claims against each other.”
How this differs from a single “invoice”
In the English-speaking world, an invoice is a hybrid. It is both the request for payment and the record of what was delivered. One document covers both cases.
The two-tier system (invoice + completion certificate) is common in markets with a formal accounting tradition. For most solo freelancers, one certificate plus a bank statement is enough to show what happened.
Do you really need both?
It depends on your client and your local rules:
- Smaller or international clients often get by with a single invoice and no extra formalities.
- Larger corporate clients and banks frequently require both — first an invoice (to trigger the bank payment), then a completion certificate (to record acceptance of the work). That’s their internal accounting, not a universal law.
Either way, you may still want a completion certificate for your own records.
Practical tips
1. Produce both documents “just in case.” It’s two minutes of your time. No invoice — the client says “I have nothing to base the payment on.” No certificate — you have no primary record for your books.
2. An invoice without a certificate is a deposit, not income. Money in your account without a signed certificate isn’t formally closed as income yet. The certificate closes the transaction.
3. Keep PDF copies of both documents for at least 3 years. That’s a typical audit window. Five is safer.
4. Electronic signatures are valid in most places — no need to print, sign by hand, and scan.
5. For international clients, a single invoice in English is usually enough. They don’t care about local formalities — but you may still want to produce your own internal certificate for your books.
How it works in Minteo
In Minteo both documents are generated from the same data:
- Create an invoice → you get two buttons: “Download invoice” and “Download completion certificate”.
- Send the client a public link → they download whichever they need themselves.
- Set up your business details once — they’re filled in automatically on every future document.
No Excel sheets, no Word templates. Set it up once, and each new document is generated in 30 seconds.