Principal residence changed to rental and back

I have a new client who purchased his residence in 2010 and lived in it until 2014 when it wasthen rented out while he was posted to another city.
There was no deemed disposition made in 2014 and there was no CCA taken for the rental years.
They will be moving back to their residence in 2022.

From what I see we can late file the 45(2) from 2016 to 2021. ( 4 plus one year). I gather this is just a letter to CRA requesting this change or is a T2091 also required.?
What needs to be done for years 2014 and 2015?
Thank you

Late file?
Did the new client have a professional file their T1-2014 or were they doing it themselves?

From the description it sounds like, if they want an election, the election late file penalties are the lesser of (1) $7,200 (72x$100) and (2) $8,000

They will need to do their calculations and choose what they want to do.

If there’s a loss they can ignore the principal residence designation and leave it as a capital property. Rare, but it does happen (currently a LOT in Calgary). No one is forced to make a PR designation.

In addition to Joe and Don’s comments, note that the 45(2) election DELAYS the change-in-use provision - it doesn’t give the taxpayer the right to pick any 4 years of the last 7. That is, if requested by the taxpayer, and accepted by the MNR, the change-in-use date would be moved from 2014 to 2018. You couldn’t use it to cover a period of 2016-2020, etc.