Basel III plus FINMA tightening: What mortgage borrowers need to know today

The Swiss mortgage market has experienced two parallel waves of regulation in 2025, whose combined effects are only now fully unfolding. Since January 1, 2025, Swiss banks have been subject to stricter Basel III capital requirements, and since May 2025, FINMA Supervisory Notice 02/2025 has further clarified credit granting practices and property valuations. The two sets of rules are interlinked. Anyone taking out, renewing, or increasing a mortgage in 2026 will encounter a different environment than just 18 months ago. The impact is particularly noticeable for investment properties, buyers with atypical incomes, and high loan-to-value ratios. This article explains the cumulative effect and shows what action options remain.

What Basel III specifically requires of Swiss banks

The Basel III framework of the Bank for International Settlements aims to increase banks’ resilience to credit risks. For Swiss institutions, this specifically means they must back mortgage loans with more regulatory capital, depending on the risk profile of the property and the borrower. The range is wide. For an owner-occupied property with low loan-to-value and prime credit, the capital requirement can even decrease. For an investment property with high loan-to-value, average location, and fluctuating tenant profiles, however, it rises significantly.

Banks do not bear the increased capital requirements themselves but instead pass them on to customers via interest margins. Anyone operating in a higher-risk segment will see this directly in the offered terms. A markup of 20 to 60 basis points is observable for investment properties in more challenging locations with loan-to-value ratios above 60 percent. Prime clients purchasing owner-occupied homes, on the other hand, benefit from slightly better margins because this segment has become more capital-efficient for banks.

What FINMA Guideline 02/2025 additionally stipulates

Supervisory Notice 02/2025 from May 2025 targets the credit granting practice itself. FINMA had identified weaknesses in property valuation, consideration of sustainable income, and the treatment of second homes and vacation properties in its audits. The guideline specifies how banks must address these points going forward. First, valuation models are reviewed more stringently. Pure reference values from a recent comparable transaction no longer suffice if market conditions have changed. Second, when calculating affordability based on income, banks must pay closer attention to income sustainability. Bonuses, commissions, and sideline earnings are given less weight. Third, there are tighter amortization requirements for investment properties.

The effect of the FINMA guideline is not limited to the interest rate side but often appears in the valuation process itself. Anyone seeking to finance a property today must expect a more conservative loan base than in 2024. A property priced by the seller at 1.5 million francs may only be deemed eligible for lending by the bank at 1.3 or 1.35 million francs. The buyer must provide the difference as additional equity.

The cumulative effect on various buyer profiles

The two sets of rules have additive effects on some buyer profiles and little effect on others. What sector self-regulation left open for years has now been closed by the new regulations. Institutions exercise less discretion than in the past because the supervisory authority is stricter. This affects market segments with varying intensity.

Prime clients with owner-occupied homes, loan-to-value ratios below 60 percent, and clean income situations are barely affected by the tightening. They often receive better conditions than before 2025, as banks actively court this customer segment. Buyers with loan-to-values close to 80 percent, variable incomes, or properties in average locations, however, face both higher margins and more conservative valuations. Access to financing is not impossible, but the process is more demanding and the terms less attractive.

Investment properties: Where the tightening hits hardest

Investors in investment or rental properties are the most affected. Basel III and the FINMA guideline here are almost entirely aligned. For an apartment building in an average location with 70 percent loan-to-value, today’s rates are about 40 to 80 basis points above rates for comparable owner-occupied properties. Valuations are often more conservative as well, especially if rents are above the regional average or if refurbishment is imminent.

Amortization requirements have also become stricter. Where previously a reduction to two-thirds loan-to-value over ten or more years was acceptable, many banks today require shorter repayment terms and higher direct amortization rates. For institutional investors, this is less painful operationally, because they can service the capital from current cash flow. For private investors with a single investment property, it means a significant impact on liquidity planning.

Self-employed and atypical incomes

The sharper assessment of sustainable income particularly affects the self-employed and people with variable income components. Banks now calculate affordability more on the basis of multi-year averages, often the last three years. Bonuses are often only credited at 50 or 60 percent. Commissions and income from sideline activities are sometimes excluded entirely from the calculation. For many self-employed people, this noticeably reduces the effective credit base.

In practice, this means that anyone self-employed seeking a mortgage should have the annual financial statements for the last three business years ready, plus an interim balance sheet for the current year. Banks also expect transparent information regarding private withdrawals, pension contributions, and hidden reserves. Anyone who prepares these documents professionally significantly improves their initial position.

Impacts on interest margins and price formation

Across the entire market, the cumulative regulations lead to a widening of conditions. The difference between the cheapest and most expensive offer for the same situation has increased. For a ten-year fixed-rate mortgage, the spread between the prime offer and the rate for an investment property with a high loan-to-value is often 100 basis points or more. Before 2025, such spreads were less common. Comparison shopping is often even more worthwhile in a regulated market than in a free one, because the interpretation of the rules varies between institutions.

Long-term fixed-rate mortgages have also been influenced by global capital market rates. In the twelve months since early 2025, ten-year rates have risen in international comparison, partially eclipsing the Swiss regulatory premium. SARON mortgages continue to benefit from the National Bank’s zero interest rate policy and remain relatively attractive for many scenarios.

Concrete courses of action for mortgage borrowers

Those currently financing or renewing should prioritize three points. First, compare several institutions—ideally through an independent broker, who contacts more than just the main supplier. Second, actively manage the loan-to-value ratio. Where possible, keep the share of borrowed capital below 65 percent, as both Basel III and the FINMA guideline are noticeably less strict in this range. Third, provide early and proper documentation of income. Those who can demonstrate the sustainability of their income avoid many follow-up questions and speed up the process.

For investors in investment properties, structuring also matters. Dividing several properties among different institutions can diversify credit risks and strengthen negotiating positions. Combinations with institutional financiers such as insurance companies or pension funds are becoming more attractive again for larger properties, because their terms have become more competitive under the new regulations. For details on the current market environment, cash.ch summarized in its analysis "Mortgages in Transition".

Outlook

Regulation is not finished with Basel III and FINMA Guideline 02/2025. Further clarifications on the treatment of sustainable rentability and climate risks in real estate have been announced. For mortgage borrowers, the basic mechanics remain the same: those who bring a solid equity base, properly documented income, and a clearly valued property can still obtain attractive conditions. Those operating in border areas must expect more effort, tougher valuations, and higher terms. The era of loose self-regulation is over; evaluation is stricter but also more predictable.

This article represents a general market observation and does not constitute individual financing or legal advice. The specific assessment of a case depends on the choice of provider and the individual's situation.