CRA acknowledges general deductibility of legal fees incurred for periodic support (but not for a lump sum settlement)
CRA acknowledges that legal fees incurred in order to make a (non-frivolous) claim for periodic support will generally be deductible in computing the claimant’s income even if the amount ultimately awarded is a lump sum that therefore (generally) does not qualify as a “support amount” – and that, conversely, legal fees incurred in order to claim a lump-sum payment that does not qualify as a support amount generally will not be deductible.
Neal Armstrong. Summary of 25 July 2019 External T.I. 2018-0787011E5 under s. 18(1)(a) – legal fees.