Can I claim costs associated with buying a house in 2018 for a move that happened in 2015?

According to the CRA website, “If your moving expenses were paid in a year after the year of your move, you can claim them on your return for the year you paid them against employment or self-employment income earned at the new work location. This may apply if your old home did not sell until after the year of your move.” https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/line-219-moving-expenses/you-claim-moving-expenses-11.html

However, I would recommend consulting with the CRA to see if your moving expenses qualify. https://turbotax.community.intuit.ca/replies/2647704