If you bill more than $30,000 per annum you are required to register for GST.
Start collecting GST
In the month following the quarter when a business exceeds $30,000 in sales, it must start collecting GST. Consider retaining a Canadian income tax lawyer for assistance.
"This article provides information of a general nature only. It is only current at the posting date. It is not updated and it may no longer be current. It does not provide legal advice nor can it or should it be relied upon. All tax situations are specific to their facts and will differ from the situations in the articles. If you have specific legal questions you should consult a lawyer."