I have a corporation registered in BC, Canada. I provide custom software development services to companies outside of Canada. Do I need to collect GST/PST ?
If you charge clients outside of province, you don't need to collect PST, and if outside of Canada, you don't need to collect GST.
Generally, GST/HST registrants must charge and account for the GST on taxable supplies (other than zero-rated supplies) of property and services made in Canada. However, where GST/HST registrants make taxable supplies (other than zero-rated supplies) in Canada, and those supplies are made in a participating province, they must charge and account for the HST instead of the GST.
PS: I think you should consult with Canada Revenue anyway. From my experience: I had sole proprietorship in Quebec, when I had clients from Ontario, I collected only GST, when I had clients in US, I didn't collect taxes at all.