ATO Certified Response
Author: NikkiATO(Community Moderator)Community Moderator ATO Certified Response20 Feb 2026
Hi @DerekW,
You’re only entitled to a partial main residence exemption if both of the following apply:
- an area of your home is set aside and used exclusively as a place of business, and
- you’re able to claim occupancy expenses (for example, mortgage interest, council rates, rent) for that area.
If you didn’t have a specific area set aside exclusively for business and you didn’t claim occupancy expenses, the main residence exemption isn’t affected. CGT doesn’t apply on sale because of that limited business use.
If you later set aside a room exclusively as a place of business and can claim occupancy expenses, the exemption becomes partial from that point. Small business CGT concessions may be available if eligibility criteria are met.
You can use the CGT property exemption tool to calculate the portion of your home that may be subject to CGT if your circumstances change.