SNB: what the September decision really changes for your mortgage and savings

SNB September 2026 decision: simulations for your mortgage and savings

Document not approved for publication. The SNB calendar, the latest applicable policy rate and any September 2026 decision could not be consulted. This text therefore presents neither an official outcome nor an announcement confirmed as forthcoming. No date of factual verification is claimed.

What would an interest rate change mean for your budget? The simulations below quantify a change in the customer rate, without presuming the outcome of the SNB September 2026 decision or how it would feed through to a mortgage or savings account.

To establish the consequences of this monetary policy assessment, you need to know the officially decided rate, the latest rate applicable beforehand, the change in basis points, the effective date and the terms of your contract. These official data have not been established in this version.

SNB September 2026 decision: distinguishing announcements from simulations

Three scenarios, not a presumed decision

The change is calculated as follows: new rate minus previous rate. For example, a hypothetical move from 0.50% to 0.25% corresponds to −0.25 percentage points, or −25 basis points. It is not a 25% reduction.

These figures are fictional: they represent neither the currently applicable rate nor an outcome announced for September 2026.

Which documents establish the outcome?

The official calendar of the Swiss National Bank must establish the date of the assessment. The corresponding press release must document:

• the announced rate;
• its effective date;
• the main reasons for the decision;
• the published forecasts and their assumptions.

The latest rate applicable beforehand must be established separately, also checking for any intervening decision.

The SNB press releases section provides access to publications, not proof of the status or outcome of the September 2026 assessment. Without consulting the specific documents, no conclusions about timing or figures are drawn here.

CHF 800,000 mortgage: three quantified scenarios

What would be the effect of a change in the customer rate on interest costs? For a loan of CHF 800,000, here are three scenarios independent of the outcome of the September assessment.

A simulation with constant principal

Author’s calculations based on fictional assumptions:

• Constant principal: CHF 800,000, with no amortisation.
• Hypothetical initial customer rate: 1.50% per year, including the bank’s margin.
• Unchanged bank margin and full pass-through of the assumed change to the customer rate.
• Fees excluded and the rate in each scenario applied for a full year.

The formula is simple: principal × annual rate. To measure the difference between two scenarios:

Change in annual interest = principal × change in the rate.

Thus, 25 basis points correspond to 0.0025 in decimal form:

800,000 × 0.0025 = CHF 2,000 per year, or around CHF 167 per month.

The monthly amounts are budget equivalents calculated by dividing annual interest by twelve. They do not represent a contractual billing schedule.

SARON mortgage: which terms should you have confirmed?

SARON — Swiss Average Rate Overnight — is an overnight reference rate for the secured Swiss franc money market.

Source on the reference rate: [SIX, “Swiss Reference Rates”](https://www.six-group.com/en/products-services/the-swiss-stock-exchange/market-data/indices/swiss-reference-rates.html). This documentation does not replace the terms of a bank mortgage contract.

To apply a simulation to your SARON mortgage, ask your bank for a dated product factsheet and the terms applicable to your contract. Have it clarify:

• the customer rate formula and the role of compounded SARON in that formula;
• the calculation period and method;
• the margin and the conditions for changing it;
• whether a floor exists and which component it applies to;
• billing dates and arrangements;
• the commitment period;
• conversion options and exit conditions.

The simulation alone cannot predict your bill. To use it, you must check that its assumptions match the terms of your contract.

Fixed-rate mortgage: comparing your existing contract with new offers

A useful comparison must distinguish commitments already signed from a new financing proposal.

Existing contract or new offer: two separate checks

For an existing fixed-rate mortgage, find the clause in your contract defining the agreed rate, how long it applies and any exceptions. If your financing comprises several tranches, examine each separately.

For a new mortgage or a mortgage renewal, request a written offer stating:

• the proposed customer rate;
• the financing term;
• how long the offer is valid;
• the amortisation arrangements;
• the fees;
• the conditions for entering into and terminating the agreement.

Without identified documentation, it is not possible to attribute a particular offer to swap rates, market expectations, funding or hedging costs, the margin or the borrower’s risk profile. No such explanation is adopted here for any institution.

Compare the actual cost before signing

Author’s calculation based on fictional assumptions: on CHF 800,000, a fixed-rate offer that is 0.25 percentage points lower reduces interest by CHF 2,000 per year, with constant principal and excluding fees. This saving results from the difference between the offers, not automatically from the SNB’s decision.

Compare proposals with identical terms, for the same amount and the same amortisation profile.

Before any early exit, request:

• the applicable contractual clause;
• a written, dated statement of penalties and fees;
• the calculation formula and the values used;
• the statement’s validity period.

Compare the exit cost with the total expected savings over the same period, not just the annual savings.

Savings account: quantifying a change in the customer rate

To calculate your interest earnings, request the rate schedule applicable to your account, including its effective date, along with the corresponding general and specific terms and conditions.

Separate the rate scenario from the account terms

The following calculations assume no rule governing pass-through from the SNB policy rate to your account rate.

They establish neither the date of any change by a bank, nor its size, nor the possible application of a negative rate. These elements must be documented in the terms or a dated communication from the institution concerned.

No commercial motive is attributed to a bank without an identified communication.

What do 25 basis points represent on CHF 50,000?

Author’s calculations based on fictional assumptions: with a customer rate change of 0.25 percentage points, on a constant balance of CHF 50,000 over a full year:

• an increase adds CHF 125 in gross interest;
• a decrease removes CHF 125 in gross interest;
• an unchanged customer rate leaves interest unchanged.

This calculation assumes that the new rate applies to the entire balance for twelve months. It does not model a mid-year change, different rates for different balance tiers or a temporary promotion.

Compare more than the advertised rate

To compare two accounts, request their current terms and check:

• The rate’s effective date and the conditions for changing it.
• Whether a promotion exists, its duration and eligible deposits.
• Whether interest rate tiers apply according to the balance.
• Withdrawal conditions: available amount, any notice period and fees.
• Account fees and fees for any mandatory associated services.

This list is a checklist, not a description of a specific banking product. Compare the return net of fees for your amount and investment period, as well as access to the funds.

FAQ: useful questions for your budget

What is the outcome of the SNB’s September 2026 decision?

This version does not establish it. The official calendar and corresponding press release have not been consulted, so it cannot confirm either the status of the assessment or its outcome.

Does a cut of 25 basis points reduce my interest by 25%?

No. It represents 0.25 percentage points. If your customer rate falls from 1.50% to 1.25%, interest on CHF 800,000 decreases by CHF 2,000 over a full year, with constant principal and excluding fees.

Should you switch mortgages or accounts immediately?

An arithmetic simulation alone is not enough to decide. Compare the expected benefit with documented fees, contractual constraints and your liquidity needs. For a mortgage, also assess your ability to cope with higher interest costs.

Conclusion: three steps before deciding

For your budget, simulations must focus on the actual change in the customer rate.

1. Reread your contract and the applicable rate schedules. Check the rate clauses, dates, fees and exit or withdrawal conditions.
2. Ask your bank for a written simulation. Have it quantify several rate levels and their effect on your budget, based on the exact terms of your contract.
3. Compare equivalent offers. The same amount, term and amortisation, with fees included, for mortgages; the same balance, time horizon and access to funds for savings.

The simulations presented here are neither banking offers nor a personalised recommendation.