What the retroactive buy-back allows
Until now, an unused 3a year was lost for good: you could not make up a forgotten contribution. The new scheme changes this by allowing you, under conditions, to fill past gaps with an additional, and also deductible, payment. It is an opportunity above all for those who had periods without contributions (early career, studies, irregular income).
The conditions to meet
The buy-back follows precise rules. You must be enrolled in 3a and have earned income subject to AHV during the years concerned. Above all, a buy-back is only possible once you have paid the ordinary ceiling for the current year; the retroactive top-up is added on, within an annual limit. Years that are too old or predate the scheme cannot be bought back.
What is the tax benefit?
Like a standard 3a contribution, the buy-back lowers your taxable income in the year it is made. Well managed, it lets you smooth an income peak (a bonus, a sale, an exceptional year) and absorb a one-off tax charge. The effect is stronger the higher your marginal rate in the year of the buy-back.
Should you go for it?
A buy-back makes sense if you have the savings capacity and a clear provision or optimisation goal. It makes less sense if your liquidity is already tight. As always with the third pillar, the trade-off depends on your horizon, your canton and your tax rate: it pays to run the numbers before deciding.