Can I be personally liable for my corporation's unpaid HST as a director?

Yes. Under the federal Excise Tax Act, directors of a corporation can be held personally liable for the corporation's failure to remit net tax (HST). This is parallel to the director liability rules for unremitted payroll source deductions under the Income Tax Act. The CRA can pursue directors personally once it has made reasonable efforts to collect from the corporation.

The Excise Tax Act provides a due diligence defence: a director is not liable if they exercised the degree of care, diligence, and skill that a reasonably prudent person would have exercised in comparable circumstances to prevent the failure to remit. In practice, this defence is difficult to establish once the corporation has actually failed to remit — demonstrating that you took concrete steps to ensure remittance (rather than simply being unaware of the problem) is required.

There is also a two-year limitation period: the CRA must assess a director within two years of the director ceasing to be a director. If you resign from a board or the corporation is dissolved, the clock starts running. Getting tax law advice immediately if you become aware that your corporation has unremitted HST is essential — especially before you sign anything that could restart limitations.