To invoice correctly in Finland, your invoice needs the particulars required by the Finnish VAT Act (arvonlisäverolaki), a clear payment term and a due date. There are more than a dozen mandatory details. A payment term to another business can run longer than 30 days only if you have expressly agreed on it. Late business invoices carry 10.5% interest from 1 July to 31 December 2026, and every invoice is kept for at least six years. This guide walks through invoicing in the order it happens: what goes on the invoice, when the money should arrive, what an e-invoice (verkkolasku) really is, and what to do when a customer does not pay.

What does a Finnish invoice have to include?

The mandatory particulars come from section 209 e of the VAT Act. They are the same whether you invoice from software or from a spreadsheet, and whether your company is a toiminimi (sole trader) or an osakeyhtiö (Oy, limited company).

A full invoice shows:

• the invoice date

• a unique sequential number (the invoice number)

• the seller's VAT identifier, which for a domestic sale is the Business ID (Y-tunnus)

• the buyer's VAT number, when the sale is under reverse charge or to another EU country

• the names and addresses of both the seller and the buyer

• the quantity and type of goods, or the extent and type of services

• the date of delivery or of the service

• the taxable amount per VAT rate, the unit price excluding VAT, and any discounts

• the VAT rate and the amount of VAT payable

• the reason for exemption or a reference to the law, if the sale is VAT-exempt

If the invoice total including VAT is at most €400, simplified particulars (kevennetyt laskumerkinnät) are enough: the date, the seller's name and Business ID, the type of goods or services, and the VAT amount or the taxable amount per rate.

Every item, with examples of what goes wrong, is in our article on what an invoice needs to include in Finland.

When do you have to send the invoice?

For ordinary domestic sales, the VAT Act sets no deadline for issuing an invoice. The exception is sales to other EU countries: for goods delivered to a VAT-registered buyer in another member state, and for services taxed in the buyer's country under reverse charge, the invoice must be issued by the 15th day of the month after the month of delivery.

In practice, sending the invoice the day the work is done matters more for cash flow than any rule. A week's delay in invoicing is a week's delay in getting paid, and it repeats on every invoice.

How long a payment term can you give?

Between businesses, a payment term longer than 30 days is valid only if it has been expressly agreed. This comes from section 5 of the Act on Payment Terms in Commercial Contracts (maksuaikalaki, 30/2013). The act sets no fixed upper limit for business-to-business terms, but a term that is unreasonable to the supplier can be adjusted under section 9.

When the debtor is a public contracting entity (hankintayksikkö), such as a municipality or a government agency, the payment term is at most 30 days. It can be extended to at most 60 days, and only if expressly agreed (section 4).

Write the payment term on the invoice in plain words, for example "14 days net". A due date with no payment term leaves room for interpretation if there is ever a dispute.

How much late payment interest can you charge?

From 1 July to 31 December 2026, the reference rate under the Finnish Interest Act (korkolaki) is 2.5%. Two late payment interest rates follow from it.

The commercial rate (section 4 a of the Interest Act) applies to invoices between businesses and to invoices where a public entity is the debtor. The Bank of Finland (Suomen Pankki) confirms the reference rate twice a year, on 1 January and 1 July, so check the current rate before you print a percentage on an invoice.

On a late business invoice you can also claim a fixed €40 compensation for recovery costs. The right arises when the right to late payment interest arises, and it applies to each overdue invoice separately. Other collection costs can only be claimed to the extent they exceed €40 (Debt Collection Act, perintälaki, section 10 i).

How to calculate interest to the day, and how to word your payment terms, is covered in our article on payment terms and late payment interest in Finland.

Which VAT rate goes on the invoice?

Finland has three positive VAT rates (arvonlisävero, ALV) in 2026.

If one invoice has lines at different rates, each line shows its own rate, and the taxable amount is shown separately for each rate, never as one total. The full rate list is in our article on Finnish VAT rates in 2026.

You have to register for VAT when your turnover exceeds €20,000 in a calendar year, checked against both the current and the previous calendar year. The threshold rose from €15,000 to €20,000 on 1 January 2025, and the small business VAT relief (alarajahuojennus) was abolished at the same time. Our article on when you have to register for VAT in Finland explains the two-year rule.

How do you calculate VAT on an invoice?

VAT is calculated from the price excluding VAT. The VAT amount is the net price multiplied by the rate.

Example at the general rate. A consultant invoices 10 hours at €90 an hour.

Example at the reduced rate. A restaurant invoices €600 excluding VAT for catering. Restaurant and catering services are taxed at the reduced 13.5% rate, not the general one.

If you agreed on a price including VAT, divide it by 1.255 at the general rate or by 1.135 at the reduced rate to get the net price. So €1,129.50 including VAT is €900.00 net plus €229.50 VAT.

The most common error here is not the arithmetic. It is the wrong rate. For both directions of the calculation, see our article on how to calculate Finnish VAT.

What is a Finnish e-invoice and when do you have to use one?

An e-invoice (verkkolasku) is a structured invoice file that moves from one invoicing system to another. A PDF sent as an email attachment is not an e-invoice, even though it is electronic.

The Act on Electronic Invoicing by Contracting Entities and Traders (241/2019) has applied since 1 April 2020. Since then, a buyer that is a business or a public entity has had the right to demand an e-invoice that meets the European standard. The right does not apply to sellers with turnover of €10,000 or less, and you never have to send an e-invoice to a consumer.

So it is the buyer's right, not a universal obligation. If you sell to companies or the public sector, a customer can ask for an e-invoice, and you have to be able to send one. NoCFO sends and receives e-invoices. The details, including what an e-invoice address is, are in our article on e-invoicing in Finland.

What is a reference number and do you need one?

A reference number (viitenumero) is not a mandatory particular under the VAT Act, but it is the single most useful field for matching payments to invoices.

The payer enters the reference number with the payment, and the bank passes it on, so the payment can be matched to the right invoice automatically. Without it, matching is done by hand from the payer's name and the amount, and partial payments or customers with similar names cause mistakes.

The last digit of a Finnish reference number is a check digit calculated from the others. A number you make up yourself will not work: it has to be generated with the right formula, which invoicing software does for you.

How do you correct a wrong invoice?

You do not edit an invoice that has already been sent. You issue a credit note (hyvityslasku) that refers to the original invoice, and then send a new, correct invoice.

The reference to the earlier invoice is a mandatory particular on a correcting invoice. It is also the first thing your accountant or a tax auditor looks for: without it, nobody can tell which of the two invoices is valid.

If the mistake is a typo in the customer's name and does not affect the VAT or the amount, a new invoice is enough. If it concerns the amount, the rate or what was sold, you need the credit note.

When does an invoice need a reverse charge note?

Under reverse charge (käännetty verovelvollisuus), the buyer reports and pays the VAT instead of the seller. The invoice then shows no VAT amount. Instead it carries a reverse charge note and the buyer's VAT number.

The two situations a small Finnish company meets most often are domestic reverse charge in the construction sector and selling services to a VAT-registered business in another EU country.

The note is mandatory. Without it the invoice is incomplete, and the buyer can ask for a new one, because they need the note for their own VAT return.

How do you invoice a customer in another EU country?

When you sell to a VAT-registered business in another EU country, the invoice must be issued by the 15th day of the month after delivery, and it must show both your VAT number and the buyer's. Your Finnish VAT number is FI followed by the eight digits of your Business ID, without the hyphen.

For goods, the sale is a VAT-free intra-community supply when the buyer is VAT-registered in another member state and the goods are transported there from Finland. For services, the main rule is that the VAT is reported in the buyer's country under reverse charge.

Selling to consumers in other EU countries follows different rules, often distance selling, and should not be worked out from the business-to-business rules. Our article on EU and export sales under Finnish VAT covers both.

Does your company form change how you invoice?

The mandatory particulars are the same for a toiminimi and an osakeyhtiö. The VAT Act looks at the seller and the buyer, not the company form.

There are two differences. Income invoiced by a toiminimi is the owner's business income and is taxed in the owner's personal taxation, while an osakeyhtiö's sales are the company's income, from which the founder takes salary or dividends. VAT registration works the same way for both: the €20,000 threshold applies to either form. If you are still choosing, our comparison of toiminimi vs osakeyhtiö sets out the trade-offs.

A light entrepreneur (kevytyrittäjä) who invoices through an invoicing service does not invoice in their own name. The invoicing service issues the invoice under its own Business ID and is responsible for the particulars.

How long do you have to keep invoices?

Invoices are accounting vouchers (tositteet), and they must be kept for at least six years from the end of the calendar year in which the financial year ended. The same applies to sales and purchase invoices. The books themselves, meaning the general journal, general ledger and financial statements, are kept for ten years (Accounting Act, chapter 2, section 10).

Electronic storage is fine, as long as the invoices stay readable for the whole period.

Keeping invoice numbering and retention in one system is what makes a tax audit short: one unbroken sequence, every voucher in one place.

What do you do when a customer does not pay?

The first step is a payment reminder (maksumuistutus). It is a plain message that names the original invoice, the due date, the interest accrued so far and a new payment date. On a business invoice you can add the €40 fixed compensation, in which case no separate reminder fee is charged on top of it.

If the reminder does not work, the next options are a collection agency or a claim in the district court (käräjäoikeus).

Most late payments are not unwillingness to pay. The invoice went to the wrong person in the customer's accounts payable, or the reference number was typed wrong. A clear invoice is the best collection tool you have.

What do you do when a customer disputes the invoice?

A disputed invoice is not the same as an unpaid one, and it is handled differently. A disputed claim does not go to a collection agency, because a collection agency does not settle a disagreement about content.

The first question is what the disagreement is about: the amount, what was delivered, or whether the work was ordered at all. Each of those is settled with different evidence.

This is where well-written invoice lines pay off. "Consulting, September, €4,500" is hard to defend. "Checkout payment API specification, 30 hours at €150 an hour" says what was done and at what price, and it can be checked against the order.

If talking does not settle it, the next step is a written response and, if needed, a claim in the district court. An unpaid claim can also become time-barred, so send reminders in writing and keep proof that they were sent.

How does an invoice connect to your books and your VAT return?

A sales invoice is an accounting voucher. One invoice produces three things: revenue in the income statement, a receivable on the balance sheet, and VAT payable on your VAT return.

That leads to a rule that matters more than it sounds. The invoice belongs in the books for the month the sale belongs to, not the month the customer pays. On the accrual basis (suoriteperuste), the sale is recorded when it is delivered, and the payment clears the receivable separately.

When invoicing and bookkeeping run on the same platform, this happens on its own. When they live in different places, someone has to move the data across and reconcile it, and that someone is usually the founder on a Sunday evening.

What recurring deadlines does invoicing create?

Invoicing brings a few recurring obligations that are worth knowing in advance.

• VAT return. Filed in OmaVero (MyTax) according to your tax period (verokausi). On monthly filing, the return and payment are due on the 12th day of the second month after the month of sale. Quarterly and annual filing have their own dates, set out in our article on Finnish VAT return deadlines.

• EC sales list (yhteenvetoilmoitus). Filed monthly with the Finnish Tax Administration (Verohallinto) if you sell goods or services to VAT-registered buyers in other EU countries.

• Year end. Open receivables are reviewed when the financial year closes, to judge which are still likely to be paid. Easy if payments have been matched all year, slow if they have not.

What goes wrong most often?

Four mistakes come up in small companies more than any others.

1. Broken invoice numbering. Some invoices come from software and some from a spreadsheet, and the sequence is no longer sequential.

2. VAT shown as one total. The invoice has lines at different rates, but the taxable amount is not split by rate.

3. No payment term. The invoice has a due date only, and in a dispute the question moves to contract terms that were never written down.

4. Payment not matched. The invoice was sent correctly, but the payment was never matched to it. The founder thinks the invoice is still open and sends a reminder to a customer who has already paid. That is the fastest way to lose a good customer.

When is it time to use invoicing software?

The time to move to invoicing software is when you send more than a few invoices a month, or when a customer asks for an e-invoice.

An invoice made in a spreadsheet is not illegal, but it leaves three things to your memory: sequential numbering, the VAT split by rate, and which invoices are still unpaid. Those three are also what cause the most questions at year end. Even free invoicing software should handle all three.

Frequently asked questions

Can I send an invoice as a PDF by email in Finland?

Yes, if the customer accepts it. A PDF is not an e-invoice, though, so a business customer can require a European-standard e-invoice instead.

What is the minimum an invoice has to show if the amount is small?

If the total including VAT is at most €400, simplified particulars are enough: the date, the seller's name and Business ID, the type of goods or services, and the VAT amount or taxable amount per rate.

How long a payment term can I give another business?

A term longer than 30 days is valid only if it has been expressly agreed. There is no fixed cap for business-to-business terms, but an unreasonable term can be adjusted.

What is the late payment interest rate in Finland in 2026?

From 1 July to 31 December 2026, the general rate is 9.5% and the rate in commercial contracts is 10.5%. The Bank of Finland confirms the reference rate every six months.

When do I have to register for VAT in Finland?

When your turnover exceeds €20,000 in a calendar year.

How long do I have to keep invoices in Finland?

At least six years from the end of the calendar year in which the financial year ended.

Why should invoicing live on the same platform as your finances?

An invoice is not just a file that goes to a customer. It is an accounting voucher, a line on your VAT return and a receivable that either arrives in your bank account or does not. When those live in three places, you spend your time joining them up.

NoCFO is the all-in-one AI-native finance platform for entrepreneurs and founders. Invoicing, bookkeeping, payroll and reconciliation run in one place, so an invoice you send appears in your books without a separate transfer. The platform does the routine work and you or your accountant stay in control: NoCFO suggests, a person reviews and approves.

For VAT beyond the invoice, see the complete guide to Finnish VAT. To send your first invoice, start free at nocfo.io.

Sources (checked 29 September 2026)

• Verohallinto: Laskutusvaatimukset arvonlisäverotuksessa (mandatory particulars, simplified invoices up to €400, EU invoicing deadline, reverse charge note)

• Verohallinto: VAT rates (25.5%, 13.5% and 10% in 2026)

• Suomen Pankki via STT: Korkolain mukainen viitekorko ja viivästyskorot 1.7.–31.12.2026 (reference rate 2.5%, late payment interest 9.5% and 10.5%)

• Finlex: Laki kaupallisten sopimusten maksuehdoista 30/2013 (payment terms, public entities, €40 fixed compensation)

• Suomen Yrittäjät: Verkkolaskutuslaki tuli sovellettavaksi 1.4.2020 (right to an e-invoice, €10,000 turnover limit)

• Valtiovarainministeriö: Pienten yritysten arvonlisäverotus muuttuu (€20,000 VAT threshold from 1 January 2025)