Portfolio growth is modelled pre-tax

Where this applies

The three-lives comparison in the legacy calculator — rent and invest, buy, buy with a suite — grows each side's portfolio at a single annual rate with no tax on the growth.

The planner is different: it holds real accounts, and an unregistered account there is taxed on its dividends and realised gains with an adjusted cost base tracked through the plan.

Why it is stated rather than fixed

Taxing the calculator's portfolios properly needs facts the calculator never collects: the mix between interest, eligible dividends and capital gains, how much turnover there is, and which account the money sits in. Applying a single guessed rate would move the comparison without making it truer.

Because the same treatment applies to every side, the comparison between renting and buying is much less affected than either absolute figure. The absolute numbers are optimistic; the difference between them is roughly right.

If you want the taxed version, build the plan in /plan, where the accounts are real.