Now compare that to the bank account that my community member was tempted by. Every dollar of interest you earn from a bank account gets added to your taxable income and taxed at your full marginal rate. Inside a retirement account, that growth will cost you nothing. Held in an ordinary accumulation phase account it returned 8.9 per cent a year over the 10 years to June 2026. Held in the retirement phase, the same investment strategy, same fund, same underlying assets returned 10.1 per cent a year.