[prisoner24601]

I've been doing this for many years and what you have above looks correct. Line 2 on the line 12100 worksheet should be x% (your share) of reported T3/T5 interest (from a joint account) based on how much you loaned your spouse as a % of the total invested capital.
When I look at my past returns (prepared by an accountant) the federal worksheet is slightly different and there is room for more details like the % split on T3 & T5 interest income. The worksheet provided by CRA online appears to have been simplified starting in the 2021 tax year. The worksheet is not filed but it is nice to have the detail recorded to to justify the number that goes in box 12100 in case CRA asks. I assume this modified worksheet (with additional detail) is specific to the tax filing software people use.

 

[prisoner24601]

What you SHOULD be doing is having separate investment accounts for each spouse. Just saves a lot of time and explanation when dealing with CRA.

I suppose that might be easier from a tax perspective but also more time and complexity managing our investments, re-balancing, estate planning and so forth. The key issue whether 1 account or 2 is to document where the money is coming from which is the same amount of work. My method was to simply loan my spouse exactly half of any money I contributed to our joint account over the years and claim 50/50. I haven't had it questioned by CRA so far but feel if they challenged it I would be ready with the supporting documents.