Swiss Pillar 3a Retroactive Buy-In Tax Calculator 2026

A forward-looking window wearing a retroactive name

The reform's most misunderstood fact is its start date. 'Ten years back' is true only once ten qualifying years exist: in 2026 the only fillable gap year is 2025; by 2030 you can reach back to 2025-2029; the full ten-year window matures in 2035. Anyone hoping to repair a decade of missed contributions from their twenties is out of luck, and any adviser suggesting otherwise is selling.

What the rule REALLY changes is the cost of a bad year going forward. Before, a maternity year, a startup year, or a sabbatical meant that year's 3a room died on 31 December. Now it survives a decade, which converts 'max your 3a every single year' from an iron rule into a flexible one, provided you eventually have the income to catch up, and provided you remember the entry ticket: the current year must be maxed before any buy-in counts.

Nadia's numbers: what doubling the deduction is worth

A buy-in year is the rare chance to push twice the normal amount through the 3a deduction. At Nadia's 28% marginal rate the double contribution saves CHF 4,064 in one tax year; in high-tax cantons the same move at a 35-40% marginal rate clears CHF 5,000-5,800. The deduction lands against your top rate, so buy-ins are most valuable in your highest-income years, which conveniently is exactly when you can afford them.

That creates a genuine timing strategy: if you carry gap room and expect a bonus-heavy or promotion year, spend the buy-in there rather than in a lean year. Gap room does not expire for a decade, and a deduction placed against a 35% marginal rate beats the same deduction against 25% by CHF 726 per CHF 7,258, free money for choosing the right year.

The fine print that decides real cases

Eligibility in the GAP year matters, not just today: you must have had AHV-taxable income in the year the gap arose. A year spent abroad or fully out of the workforce creates no fillable room, the reform rewards under-contributing workers, not non-workers. Cross-border commuters and returning expats should check each year individually.

Partial fills are final. If your 2025 gap is CHF 7,258 and you buy back CHF 4,000 of it, the remaining CHF 3,258 cannot be claimed later, the year is considered dealt with. Fill a given year's gap completely or deliberately leave it whole for a better tax year; half-measures burn room permanently, and the calculator's gap output is sized around exactly that all-or-nothing rule.

And the old multi-account wisdom still applies on the way out: 3a balances are taxed at withdrawal, progressively, so spreading savings, buy-ins included, across two or three accounts lets you stagger withdrawals across tax years in retirement. The buy-in reform changed how money gets IN; the exit planning that saves the second round of tax is unchanged and worth setting up before the balances grow large. The two strategies compound: buy-ins maximise the deduction going in, staggered accounts minimise the tax coming out, and a saver who does both captures tax relief at both ends of the same franc.