An invoice goes unpaid in Germany — from which day can you legally add interest? Statutory default interest (Verzugszinsen) is not a bonus charge. It is the damages a creditor is entitled to under German law for the time their money was missing. The mechanics live in § 288 BGB, the start date in § 286 BGB. Apply them correctly and you have an enforceable claim; get them wrong and the court will trim the bill. The default interest calculator gives a quick, defensible number in 30 seconds.
Default interest vs contract interest — a key distinction
Default interest is statutory damages for late payment of a due monetary claim. It accrues automatically once the debtor is in default — no contractual clause needed. It is different from:
- Contract interest on a loan (the loan calculator works out the annuity from the agreed rate).
- Cash discount (Skonto) as a reward for early payment — see the cash discount calculator.
- Maturity interest under § 353 HGB (5 % between merchants from the due date, even without default).
1. When does default start? § 286 BGB
Default interest only runs from the moment the debtor is in default — which requires three things: the claim is due, the debtor has not paid, and (usually) a reminder has been sent. § 286 BGB names three situations where the reminder is unnecessary:
- Fixed payment date — invoice text such as "payable by 15 June 2026" or "14 days after delivery" is enough.
- 30-day rule (§ 286 (3) BGB) — monetary claims fall into default 30 days after the invoice was received, when the debtor is a business. Against consumers the rule only works if the invoice expressly states this consequence.
- Serious and final refusal to pay — the debtor declares they will not pay.
Practical rule: note the date of the first reminder, otherwise note the due date + 30 days. Days in default count from that date.
2. Consumer or business?
The surcharge depends on the debtor's status:
- § 288 (1) BGB — consumer: base rate + 5 percentage points. Applies whenever at least one party is a consumer (§ 13 BGB).
- § 288 (2) BGB — B2B: base rate + 9 percentage points. Applies only between businesses, with no consumer involved.
A freelancer billing a private customer can only claim 5 percentage points — even though they are a business themselves. What counts is the status of the debtor.
3. The base rate — reset every six months
The German base rate under § 247 BGB is published twice a year by the Deutsche Bundesbank (1 January and 1 July). It is not the ECB policy rate; it is derived from the main refinancing operation. Historical range since introduction:
| Period | Base rate |
|---|---|
| 2002 | 2.57 % |
| 2011 (January) | 0.12 % |
| July 2016 – June 2022 | −0.88 % |
| 2024 (January) | 3.62 % |
| 2024 (July) | 3.37 % |
| 2026 (current) | 1.27 % |
When the base rate was negative, the surcharge (5 or 9 percentage points) was the minimum default rate — the surcharge does not slide into negative territory.
4. The daily interest formula
For statutory default interest the formula is uniform and simple:
Default interest = claim × rate × days / 365
Important details:
- 365 days, not 360 — the commercial 360-day convention used for the cash discount calculation is not permitted here. Statutory default interest is computed day by day on the actual calendar.
- Leap years — if the default period falls into a leap year, divide proportionally by 366.
- Gross claim is the base — default interest applies to the gross amount (VAT included), because the VAT is part of the contractual debt.
- Default interest itself is not subject to VAT — it is genuine damages, not a service.
5. Worked example — consumer claim
A repair shop invoices € 1,500 (gross). The invoice carries the required 30-day notice, dated 1 April 2026, received on 3 April. The customer only pays on 30 June 2026 — default started on 4 May (once the 30 days from receipt had elapsed); the period to 30 June is 58 days.
| Item | Calculation | Amount |
|---|---|---|
| Base rate | Bundesbank | 1.27 % |
| Surcharge § 288 (1) | +5.00 percentage points | 5.00 % |
| Default rate | 1.27 % + 5.00 % | 6.27 % p.a. |
| Daily interest | 1,500 × 0.0627 × 58 / 365 | € 14.94 |
| Total claim | € 1,500 + € 14.94 | € 1,514.94 |
For a B2B transaction (e.g. the same workshop billing a tradesperson) the rate would be 10.27 % p.a. and interest € 24.48 — plus the € 40 flat fee under § 288 (5) BGB. A foregone cash discount cannot be folded into the default rate; the statutory rate is fixed.
6. Reminder, collection and lawyer fees
Default interest is not the only claim in a default scenario — but the other items are tightly limited:
- € 40 flat fee (§ 288 (5) BGB) — B2B only, no proof of damages required, once per invoice.
- Reminder fees — against consumers, German case law usually allows only material/postage (often € 2.50 per reminder). The first reminder is generally not refundable, because it is the precondition of default.
- Collection costs — the Federal Court (BGH) only allows them to the extent they were necessary for enforcement. For simple dunning that often covers no more than a 0.9 fee under RVG.
- Lawyer fees — refundable as default damages if the debtor would not pay otherwise. The fee scales with the value in dispute (= principal without default interest).
7. What the calculator does not cover
The default interest calculator deliberately only computes the statutory claim under § 288 BGB — principal, base rate, surcharge and days. Out of scope:
- Reminder, collection and lawyer fees — these depend on the facts and have no formula.
- A base-rate change inside the default period — for long defaults across 1 January or 1 July, the period must be split and computed with two different rates.
- Damages above the statutory rate (e.g. higher refinancing cost) — covered by § 288 (4) BGB, but requires concrete proof.
- Court fees from a formal payment order procedure.
Typical mistakes
Forgetting to send a reminder
Without a reminder and without a fixed payment date there is no default — and no single day of default interest. Anyone writing invoices should embed "payable by ..." as a standing clause.
Charging 9 % against a consumer
The higher surcharge under § 288 (2) BGB only applies between businesses. Used against a private customer, it gets cut down in the payment order.
Using the 360-day method
The commercial 360-day method is standard in banking and required for the cash discount formula, but is not allowed for statutory default interest. Always divide by 365 (366 in a leap year).
Compounding the default interest
Compounding default interest is excluded under § 289 sentence 1 BGB. The daily formula runs linearly on the principal — never on interest already accrued. For genuine compounding effects see the compound interest calculator.
Ignoring the half-year base-rate change
If the default period crosses 1 January or 1 July, the base rate often changes. The correct treatment is to split the period: days before the change with the old rate, days after with the new — then sum.
Bottom line
Statutory default interest in Germany is tightly codified — the hard part is not the maths but proving when default started and classifying the debtor correctly. Invoices with a fixed payment date cut the reminder discussion out entirely. In B2B the rate (9 percentage points) and the € 40 flat fee together are a real nudge for on-time payment. Start with the default interest calculator; for the early-payment trade-off use the cash discount calculator, and for ordinary credit interest the loan calculator or the compound interest calculator.