Unpaid invoices in Switzerland: payment reminders, default, interest and debt collection

Default: from when is the customer in default?

The debtor of an invoice that is due is in default as soon as the creditor sends a formal reminder, that is, clearly asks for payment (Art. 102 para. 1 CO). Without a reminder, the debtor is in default simply on expiry of a payment date “set by agreement”, or set by one party, by duly given notice, under a right reserved to it in the contract (Art. 102 para. 2 CO).

Default (Verzug)

The situation of a debtor who has not paid a debt that is due after a formal reminder, or on the agreed due date. It starts default interest running.

Formal reminder (Mahnung)

A clear request for payment; a precise first reminder counts as one.

Final demand (formal notice)

In practice, the last letter before debt collection. The debtor is often in default well before.

“Payable within 30 days” printed on the invoice

Its exact effect is debated, and this guide does not cite case law on the point. Two readings coexist:

• Agreed period (contract, accepted offer, accepted general terms and conditions): the due date is a day set by agreement, and default occurs when it expires (Art. 102 para. 2 CO). Justis, for example, runs interest from the due date.
• Period printed only on the invoice: the creditor set it alone, after the fact. According to WEKA, such a unilateral period is generally not enough to put the debtor in default: a formal reminder is needed.

Recommendation: agree the payment period before performing the service and send a clear, dated reminder as soon as the due date has passed. For interest, start from the agreed due date, otherwise from your first clear reminder or, to be most cautious, from the expiry of the period it grants.

Late payment interest of 5%: calculation and limits

From the moment of default, the debtor of a sum of money owes default interest of 5% per year, “even where a lower rate of interest was stipulated by contract” (Art. 104 para. 1 CO). On 16 August 2023, the Federal Council decided to keep this fixed rate rather than switch to a variable rate; the article is identical in the version already published for 1 July 2027.

Example

An invoice of CHF 10,000, in default for 45 days: 10,000 × 5% × 45 / 365 = CHF 61.64 in interest. Interest is calculated on the principal only: interest already accrued does not itself bear interest. The late payment interest and reminder calculator does this calculation and prepares the corresponding letter.

Reminder fees: only if they were agreed

Reminder fees are only owed if they were clearly agreed, for example in a contract or in general terms and conditions accepted by the customer; vague wording is not enough. No law sets a flat rate: “reminder fees of CHF 20” added automatically have no legal basis without an agreement.

Without an agreement, the creditor can only claim, on top of the 5% interest, the additional damage it can prove (Art. 106 CO). If you want to charge fees, set an amount per reminder in your general terms and conditions, and have them accepted before the order.

Payment reminder letters for an unpaid invoice: three levels

No law requires a specific number of reminders: the schedule below is common practice, not an obligation. Each letter contains three elements: what is owed, a deadline given as a specific date, and what will happen next.

Two tips on form. Write a date (“by 15 October 2026”) rather than a period (“within ten days”), whose starting point can be disputed. And send the last letter in a way that lets you prove receipt: registered post, or an email the customer acknowledges.

If the customer disputes the service itself, address the substance before going further. The templates for the three letters are ready to copy, interest included.

Debt collection in Switzerland: request for debt enforcement and payment order, step by step

The DEBA does not require any prior reminder: a reminder serves to establish default and the start date of interest, not to open debt enforcement proceedings.

1. Request for debt enforcement (Betreibungsbegehren): you file it with the debt enforcement office (Betreibungsamt), in writing or orally (Art. 67 para. 1 DEBA). It states your name and address (and those of any representative), the debtor's name and address, the amount in Swiss francs, the interest rate and start date, and the document evidencing the claim and its date or, failing that, its grounds (for example “invoice no. 2026-104 of 3 March 2026”).
2. Payment order (Zahlungsbefehl): on receipt of the request, the office draws up the payment order (“summons for payment” in the official English translation of the DEBA), which repeats these details and calls on the debtor to pay the debt and costs within 20 days (Art. 69 DEBA). It is then served on the debtor.
3. Objection (Rechtsvorschlag): the debtor can file an objection, orally or in writing, within 10 days of service (Art. 74 para. 1 DEBA). If they dispute only part of the debt, they must state the exact amount, otherwise the entire debt is deemed disputed (para. 2).
4. Continuation of proceedings (Fortsetzungsbegehren): without an objection, you can request it once 20 days have passed since service of the payment order; this right lapses one year after service (Art. 88 DEBA).
5. If an objection is filed: the proceedings are suspended. To continue them, you need a decision setting aside the objection (Rechtsöffnung), obtained through court or administrative proceedings; while those proceedings are pending, the one-year period does not run (Art. 88 para. 2 DEBA).

Before filing the request, check that the amount, the rate and the start date of interest match your final demand: the office carries them over to the payment order.

Bilateral contract: set a time limit, then choose (Art. 107 and 108 CO)

In a bilateral contract, such as a sale or a contract for work and services, the party whose counterparty is in default may set an appropriate time limit for performance (Art. 107 para. 1 CO). Once that time limit has passed, it may still demand performance and damages for the delay; or, if it declares so immediately, forgo performance and claim damages for non-performance, or withdraw from the contract (Art. 107 para. 2 CO).

No time limit is needed if the debtor's conduct shows it would serve no purpose, if late performance has become pointless for the creditor, or if the contract provided for a fixed date (Art. 108 CO).

For a service already delivered, the usual route remains payment with interest, then debt collection. Art. 107 and 108 are mainly relevant when the contract is still ongoing; the decision is best taken with an adviser.

Preventing unpaid invoices: terms, references and QR-bill

Most of the difficulties of chasing payment are settled before the invoice is sent.

• General terms and conditions accepted before the order: the payment period (default then occurs on the due date, Art. 102 para. 2 CO), the amount of reminder fees, and an interest rate if it is to exceed 5% (Art. 104 para. 2 CO).
• A unique reference per invoice: with a QR-IBAN, the 27-digit QR reference, the last digit of which is a check digit; with an ordinary IBAN, the RF Creditor Reference (ISO 11649). The reference travels with the payment: the incoming payment is matched to the right invoice, and you do not chase a customer who has already paid.
• A compliant QR-bill attached to every reminder: since 22 November 2025, only structured addresses are accepted. The customer pays the reminder without re-keying anything.

The QR-bill generator produces an invoice with a reference, and the QR and RF reference tool calculates or checks the check digit. The QR-bill guide explains which combinations of IBAN and reference are valid.

What can be automated, and what remains a decision

The hard part of a reminder is not writing the letter, it is sending it at the right time, every time, without chasing a customer who has already paid. That part automates well:

• tracking the due date of each open invoice;
• matching incoming payments with invoices, using the reference;
• preparing the reminder at the right level, as a draft, with interest calculated and an up-to-date QR-bill;
• a dated record of each letter sent, useful to prove the formal reminder;
• preparing the data for a request for debt enforcement: amount, rate, start date of interest, document evidencing the claim.

What stays human: deciding to send, handling a good customer with care, responding to a dispute, starting debt collection.

Dossivio Flows builds this kind of automation for a fixed package of hours, on your existing tools: accounting or invoicing software, email, spreadsheet. Reminders are prepared as drafts; sending remains the decision of an authorised person.