I've always played it safe when it comes to the Canada Revenue Agency. But the way the GST system is set up, if you're running a legitimate business (unless it's one with high revenues and very low expenses, and please let me know so I can get in on that!) you're crazy not to start collecting/charging GST. You get your 6% (5% soon) back on all business purchases, and as an added bonus your business looks more professional to your customers. You can register as a sole proprietor without much hassle at all, and it really doesn't take that much time or effort to keep it all straight. Also, if you're anywhere near the mandatory cutoff ($30,000 in sales for the previous 12 months), it pays to get everything set up before you get to that number, otherwise you'll end up paying the GST on some of your sales out of your pocket!