The Transfer Balance Cap (TBC) limits how much super you can move into the tax-free pension phase — currently around $2 million per person. Anything above the cap has to stay in accumulation phase, where earnings are taxed at 15% (still low, just not free).
How the planner handles it
For larger balances the model tracks super as two pools — a tax-free pension pool up to the cap and a taxed accumulation pool above it — and taxes each correctly. It also matters for the means test: super in accumulation phase is treated differently before Age Pension age. Most people never hit the cap, but for high balances it materially changes the after-tax result.