In Canada you just file capital gains or expenses for anything under how much your expense / gain was. If you get reviewed or audited you can revise your documents and you'll get more back.
It's kinda interesting because a lot of people will claim less than the levels that would normally trigger an audit (49% of household expenses towards rent, say) and then if they get audited upwards revise it to 75%. It's like a societal cheaper NASH equilibrium, since both the individual and the government gets penalised for being overzealous.
