You sound so confident that the reasonableness test should cause the mechanic no worries.  Have you ever gone through a CRA audit?  This change will empower them even more to impose their own view of what is reasonable.  Given the vagueness of the proposed legislation, good luck to the mechanic.  Many honest, hard working people will find themselves unduly penalized by CRA auditors who know nothing about operating a business.   If the mechanic says $25,000 is reasonable, but the CRA auditor thinks $20,000 is more reasonable, that extra $5,000 is taxed at the highest possible rate, and they lose the capital gains exemption.  That is a harsh penalty to impose.  You are naive if you think an auditor would  not do that.