Start with two different limits
FTA Circular 18a distinguishes the annual buy-in limit from the shortfall for each past year. There is only one buy-in per tax year, capped at the applicable small deduction even for people without occupational pension membership. One buy-in can cover several years. However, a given gap year can be addressed only once. Selecting the years matters as much as the amount requested. An unsolicited deposit in the pension account does not replace a formal buy-in request.
Do not assume two eligible gap years in 2026
Gaps before 2025 cannot be bought back under this scheme. For an application in 2026, 2025 is the only possible past year. Eligibility depends, among other things, on income subject to Swiss OASI in the relevant years, payment of the full ordinary contribution for the buy-in year and no previous receipt of a 3a retirement benefit. Check the statutory ten-year period and documentation requirements as well. A year in which you could not contribute does not become an eligible gap just because your statement shows zero.
A hypothetical example for a later year
Suppose that in 2027, after checking the applicable cap and all the conditions, someone can choose between a CHF 1,800 gap for 2025 and CHF 4,200 for 2026, but wants to use only CHF 3,500 of cash. Allocating CHF 1,800 to 2025 and CHF 1,700 to 2026 could leave CHF 2,500 for 2026 that cannot be completed through a second buy-in. Another choice would be to address only 2025 and keep the rest accessible. These figures illustrate the cost of partial allocation; they do not guarantee eligibility or a deduction.
Prepare instructions you can check later
Give each year a line with eligible income, the ceiling for that year, certified contributions, the gap and any prior buy-in. Ask the foundation to confirm the years selected, documents and payment order before transferring money. Reconcile its certificate against the list once processed. If you cannot afford to fill a particular gap, compare waiting, subject to the statutory time limit, with the effect of a partial buy-in you cannot later complete.
What if a certificate is missing?
Start with the provider that received the contribution and request the record for the relevant year. A bank statement can help reconstruct the history, but it need not be the certificate required. Reconcile records from different foundations if you moved an account. Transferring existing savings is not a fresh ordinary contribution. Confirm disputed years before including them and keep the payment references for a buy-in separate from those for the current year's regular contributions. This makes it easier to identify how each payment was booked.