Do I have to collect and remit HST if I'm self-employed in Ontario?

In Ontario, HST (Harmonized Sales Tax) is the provincial sales tax system, combining the federal GST and Ontario's provincial portion. If you are self-employed and provide taxable supplies (most goods and services), you are required to register for and collect HST once your worldwide taxable revenues exceed $30,000 in a single calendar quarter or over four consecutive quarters. Below this threshold you are a "small supplier" and registration is optional, though you can register voluntarily.

Once registered, you charge HST on your taxable sales and remit the collected amounts to the CRA. Importantly, you also get to claim Input Tax Credits (ITCs) for the HST you paid on business expenses, which can result in a net refund if you paid more HST on inputs than you collected on sales. Registration also makes you appear more established to clients and lets you recover HST on purchases immediately.

Failure to register when required can result in the CRA assessing you for uncollected HST plus penalties and interest. The HST deadline for filing and remitting depends on your annual taxable revenues — smaller registrants file annually, larger ones quarterly or monthly. Your T1 return and your HST return are separate filings with different deadlines and different processes.