Should an individual exceed their concessional contribution cap, the excess contributions are included in their income tax return and taxed at the marginal rate of the individual (less a 15% tax offset).
Should an individual exceed their non-concessional contributions cap – including making use of the bring forward rules, if applicable – the excess amount may be taxed at the maximum marginal individual tax rate, inclusive of Medicare levy. Currently this is 47% for the 2022 year and later.
Unless you choose to withdraw your excess concessional contribution from your superannuation fund, the excess also becomes a non-concessional contribution. If this new non-concessional contribution takes you over the non-concessional contribution cap, your contribution could be taxed twice. To avoid this – be aware of the contribution caps and how much you are contributing to superannuation.
(Note: An ECC charge is no longer applied after 1 July 2021.)