Should I add GST & PST on the selling price?

[pegasuseshop]

I imported some small products from overseas， and I paid the tax （GST,HST,PST ？）during the customs clearance.  Just opened the new shop under my business name at eBay , should  I ask the buyer to pay the tax as well? if so, how should I figure out the tax rate？ 

[kroutpick]

You have to be tax registered (GST/HST and/or PST) with government number to be legally authorised to collect tax.

If you're not planning to sell over 30 000 $ a year, there is no need to collect them.

As a business (self-employed person) you however have to put your ebay sellings on your income declaration.

[femmefan1946]

I gather you already are a tax-registered business? Those taxes on import turn into credits on export. Talk to your accountant.

EBay sales are usually just part of the larger B&M/web/auction/Wholesale/retail conglomerate that is a small business nowadays.