Fully agree with your observations. The liberal government introduced a fiscal change that would have capital gains after June 24 taxed at a higher rate for any amount higher than 250K. In this context I assume that every financial institution should have reported a value for box 52 and 53. But of course if your capital gains after June 24 are less than 250K (99% of Canadians I assume) then it makes no difference. You can enter it all in Box 53 and taxation will be no different.
As you've observed TurboTax expects an amount in Box 53 to calculate the applicable tax on your T3 capital gains. If you only report an amount in Box 21 then TT will not deduct any amount. I suspect that some TurboTax users with T3 capital gains reported only in Box 21 and not Box 53 could have a bad surprise if CRA recalculates their tax owing since TT did not deduct any.
Anyway this is a tricky and easily confusing topic: I understand the fiscal change was not always well understood (and lately it has been deferred to January 2026!), financial institutions haven't always updated their reporting methods and TT has a weird way to handle this. All of this this is on top of the initial problem where TT does not add correctly box 52 and 53 and this is quite bad for a broadly used tax return application. I am quite surprised TT did not fix this problem (and asked users to use a workaround).
