Anything claimed on line 22100 is recorded as an investment expense claimed in determining the CNIL balance (Cumulative Net Investment Loss).  It doesn't mean that they are a capital expense.  It does mean that should the individual claim a capital gains deduction in the future the amount will be reduced by the excess of legal fees (or other charges) claimed on line 22100 over investment income recorded. Legal fees for support payments must be claimed on line 22100 per CRA.  Note that the bold "must" is CRA's bolding, not mine.

Fees relating to support payments that your current or former spouse or common-law partner, or the natural parent of your child, paid to you must be claimed on line 22100 of your return.

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