What happens to unused FHSA contribution room if I don't open an account right away?

Unlike RRSP room, FHSA contribution room does not accumulate automatically just because you're eligible; it generally only begins building once you actually open an FHSA. If you wait to open an account, you aren't quietly banking room in the background the way you would with an RRSP based on your earned income - you simply aren't accumulating any FHSA room at all during that time.

This is one of the most commonly misunderstood parts of the FHSA, because people assume room works the same way across all registered plans, and it doesn't. Practically, delaying opening an account has a real cost: every year you wait without an account open is a year of room you cannot get back later. The Income Tax Act does allow some unused room to carry forward once an account exists, but the specifics of how much can carry forward are worth confirming directly rather than assuming you can simply catch up entirely later. If buying a first home is even a possibility down the road, opening an FHSA early, even with a small initial contribution, is generally worth doing sooner rather than later.