Since 2018–19, you've been able to carry forward unused concessional contributions cap for up to 5 years. If you didn't use the full cap in a given year, the unused portion stays available — letting you make a much bigger tax-deductible contribution in a later year.

The 5-year window

In FY 2025–26 (the current year), you can use unused cap from FY 2020–21 onwards. Each new year, the oldest year drops off — so unused 2020–21 cap is "use it or lose it" by 30 June 2026.

The $500,000 TSB test

You can only use carry-forward in a year where your Total Super Balance on 30 June of the prior year was under $500,000. If your balance grows past $500,000, you keep your unused cap on the books — you just can't use it that year. If your balance later drops back under $500,000 (markets can do that), the carry-forward becomes accessible again.

Where the tax saving comes from

A personal deductible contribution reduces your taxable income at your marginal rate, then sits in super taxed at 15%. Top marginal earners (income $190k+) save 47% − 15% = 32 cents per dollar contributed. Add Division 293 if applicable (effective contributions tax becomes 30%) — saving narrows to 17 cents per dollar but is still material.

When carry-forward is most valuable

One-off windfall years — sale of an investment property triggering CGT, large bonus, inheritance with capital gain, business sale. Career break returners (parental leave, sabbatical) often have huge unused caps. Always confirm your actual unused cap via myGov ATO services before contributing — funds can take time to report and the ATO figure is what counts. See ATO — Concessional contributions cap.