What Is a FlexLån? Denmark’s Variable-Rate Mortgage Explained

The difference between a FlexLån and a fixed-rate mortgage

Denmark’s realkredit system gives you two fundamental paths for a mortgage: lock your rate for the full term (a fastrente loan, up to 30 years), or let it reset periodically (a FlexLån). Both are realkredit loans, bond-funded, up to 80% of property value, issued by a realkreditinstitut rather than a bank.

With a fixed-rate loan, you pay the same rate from the day you sign until you sell, refinance, or hit year 30. Boring in the best possible way.

With a FlexLån, the rate is agreed for a defined period (the lock interval), then re-priced at auction when that period expires. The new rate could be lower. It could be higher. The market decides.

The appeal is obvious: FlexLån rates have historically sat below fixed-rate equivalents. Since FlexLån was introduced in 1996, borrowers on variable-rate mortgages have, in most years, paid less than their fixed-rate counterparts. But “in most years” is doing a lot of work in that sentence: 2022 and 2023 reminded a lot of Danish homeowners why fixed rates exist.

How the rate reset actually works

At each reset, your realkreditinstitut refinances by issuing new bonds. The coupon on those bonds, whatever the market clears at auction, becomes your new rate for the next period. You don’t negotiate it. You don’t opt in or out. You just get the rate the market sets.

The F1 resets every January. F3 and F5 loans typically reset 1 April or 1 October, though this varies by institution. Your loan agreement will state the exact dates.

One thing worth understanding: the reset doesn’t mean you’re getting a new loan. It means the underlying bonds are refinanced. Your loan registration (your tinglysning) stays in place. The debt amount doesn’t change. Only the rate does.

What you actually pay

Your total monthly cost has three components.

The bond coupon is the market interest rate on the underlying bonds. This is what resets at each interval.

The bidragssats is the administration margin charged by your realkreditinstitut on top of the bond rate. It covers their operating costs, risk capital, and profit. It doesn’t reset with the bond market: the institution sets it, and can change it with notice during your loan term (this has happened). The bidragssats on FlexLån is typically marginally higher than on fixed-rate equivalents, partly because variable loans require more frequent administration at refinancing.

Registration fees (tinglysningsafgift) apply at origination: a fixed fee of DKK 1,825 plus a variable component of 1.25% of the principal.

Always compare AOP (the Danish annual percentage rate equivalent) rather than the bond coupon alone. Two loans with the same coupon can have meaningfully different effective costs once bidragssats is included.

The F1 problem and why most borrowers now choose F3 or F5

An F1 loan sounds appealing: the shortest lock means you capture rate cuts fastest. In a falling rate environment, it outperforms.

The problem is that the economics shifted. Short-term bonds carry refinancing costs (kursskæring, a bid-ask spread paid at each auction). With F1, you pay this every year. On top of that, bidragssats rates on F1 loans have historically been higher than on F3 and F5, reflecting the more frequent administration.

After the rate rises of 2022-2023, many F1 borrowers found their payments increasing sharply year on year, while F3 and F5 holders had more breathing room. The refinancing auctions in late 2024 and into 2025 produced rates on some F1 loans higher than fixed-rate alternatives available at the same time, removing the main reason someone would choose them.

The result: most advisors currently point borrowers toward F3 or F5 as a better balance of rate sensitivity and stability. F1 suits borrowers who plan to sell within 12 months and want to minimise total interest paid, or those with genuinely large buffers and high risk tolerance.

Interest-only FlexLan: the afdragsfri option

A FlexLån can be structured with an afdragsfri (interest-only) period of up to 10 years, subject to your LTV staying within 60% of the property value.

During this period you pay the bond coupon and bidragssats only, no principal repayment. Monthly payments are lower. The loan balance doesn’t shrink.

Many Danish homeowners use this strategically: take interest-only in the early years when cash flow is tightest, then switch to amortising when income grows. It’s legal and fairly common. But it requires active management: if your property value falls and your LTV climbs above 60%, the interest-only option disappears until you’ve paid down enough principal to get back below the threshold.

For expats, one practical note: if you’re planning to leave Denmark within 5-10 years and sell the property, the interest-only structure means you’ll be selling with more debt than you started with. Whether that matters depends on whether Danish property prices have moved in your favour. This isn’t a uniquely expat risk, but it’s worth pricing in.

What is a rammelan, and do Danish banks offer one?

The term “rammelån” (literally: framework loan) is widely used in Norway for a revolving home equity line of credit. You get approved for a credit limit secured against your property, and you draw down and repay freely within that limit, paying interest only on the outstanding balance.

In Denmark, this product exists but goes by different names depending on the lender. Realkredit Danmarks FlexLife, for instance, combines variable-rate realkredit financing with a flexible repayment structure that allows you to dial payments up or down over the life of the loan, which edges toward the rammelan concept. Danske Bank’s Bolig Fri product operates on similar principles.

The comparison table below sets out the key distinctions.

If you’re using the word “rammelån” in conversations with a Danish bank or advisor, they’ll usually understand what you mean. Clarify whether you want a realkredit loan (FlexLån) or a bank-level credit facility, because these are structurally different products with different costs.

The stress test and what it means for you

Whatever FlexLån variant you choose, you’ll be stress-tested the same way. The lender must verify that you can afford repayments calculated at 4% over 30 years, even if your actual loan is interest-only at a lower rate.

This matters for expats in particular. If your gross income-to-debt ratio is close to the 4.0x LTI ceiling, a rate rise doesn’t just affect your monthly payment: it could affect your ability to refinance at the next reset, since the stress test is applied at each refinancing, not just at origination.

The tax deduction and how it interacts with FlexLan

Denmark allows mortgage interest to be deducted from taxable income. The deduction is automatic: your lender reports directly to Skat, it appears on your arsopgorelse, and you don’t file anything separately.

The rate of the deduction depends on the size of your interest payments.

For couples, the threshold is DKK 100,000.

The practical implication: on a FlexLån, your deductible interest changes every time your rate resets. If rates fall at your next reset, your interest payments drop and so does the value of your deduction. If rates rise, you pay more, but the deduction partially offsets it (at 33.6% up to the threshold, or 18.6% above it).

It’s a modest cushion. It doesn’t change the fundamental risk profile of a variable-rate loan. But it’s worth knowing the numbers before your next reset date.

Is a FlexLan right for you?

There’s no clean universal answer, which is why this is the point where a conversation with a mortgage adviser matters more than any article. A few honest framings to take into that conversation.

FlexLån tends to suit: Borrowers with strong income stability and real buffer capacity (not theoretical). Those expecting to sell within the fixed period, so the reset risk never lands. People entering Denmark in a higher-rate environment who believe rates will fall before their first reset.

Fixed-rate tends to suit: Those who prioritise payment predictability above cost minimisation. Borrowers with tighter LTI ratios who can’t absorb a significant payment rise. Anyone staying 10 or more years who values certainty over the possibility of saving a percentage point or two.

What happens if you want to get out early

You can redeem a FlexLån before the reset date, but you do so at market price, not at par. This is the kurs risk. If you took out the loan when bond prices were at 100 and want to redeem when they’re at 96, you need to buy back bonds at 96, meaning you’re paying to exit.

At the reset date itself, you can always redeem at par (kurs 100). So the cheapest time to sell, refinance, or switch loan type is at the exact moment of a reset, not in between.

This is a meaningful practical constraint for expats who may need to exit Denmark on relatively short notice. If your reset is in January and you’re likely to leave in April, the maths of exit costs are worth running in advance.