"How did you do the small business registration?"

???

What are you trying to register?  Why?

If you buy a few items for resale on eBay and elsewhere, no registration is required unless you want to register for HST since you live in Ontario.

HST registration is compulsary if your annual sales exceed $30,000.  Otherwise it is optional and can be beneficial if a large percentage of your sales are exported.

You still need to keep track of your sales and net profit (sales minus costs of goods sold minus related expenses) for income tax purpose.  However, no business registration is required for that purpose. 

Simply enter your annual sales on line 162 and your net profit as "net business income" on line 135 of your annual income tax return.  Attach a "profit and loss statement".  You can use the form provided by CRA or make your own.

Here is a sample of a P&L Statement I prepared a few years ago for eBay sellers:

http://pierrelebel.com/lists/P&L-sample.htm

Feel free to use it and modify it as needed for your business.

"they wrote, you must register"

You are taking the information out-of-context.

There is no need to register unless and until you run a sizable business.

On the other hand, all net profits MUST be reported for income tax purposes, regardless of amounts.

"The other benefit is tax write off"

ALL business of all sizes, registered or not, can deduct relative expenses from their sales to arrive to the net profit recorded as "business income" on line 135 of the tax return.

There is NO need to register anything anywhere to deduct expenses for tax purposes.

About "out of context":

I tried to keep it short, here is the longer, with context version:

1. eBay International Trading Policy http://pages.ebay.ca/help/policies/international-trading.html states:

"Items for commercial use: If you import goods for a commercial purpose, you may have to deal with quotas, duty, and paperwork. Commercial goods (goods intended for resale) may have special entry requirements, and it's up to you to educate yourself on the laws to ensure you're in compliance."

2. Government service hrrp://www.canadabusiness.ca/eng/126/156/ in Regulations, Licences and Permits lists Resulations for specific business activities, which provides links to how import and export are regulated, with no exceptions because of the size of the business.

3. One of the export links leads to http://www.cbsa-asfc.gc.ca/publications/pub/bsf5081-eng.html Exporting Goods From Canada

Way down the page, there is quick reference table, absolving very small exports (below $2,000) of non-restricted good.

4. I was not able to find similar thing for an import yet, only that for import you must register and only that shipments valued less than $1,600 could be delivered by Canada Post and it will charge all applicable fees, but this was clearly made for large businesses.

5. CRA states in "Do you need a program account?" http://www.cra-arc.gc.ca/tx/bsnss/tpcs/bn-ne/ndn/menu-eng.html

"Not all businesses require a Business Number (BN), so it is important that you review the information for each type of program account before registering.

You only need a BN if you require any one of the following business accounts:

GST/HS

...

Import/Export".

And so on.

Without being cranky, I prefer not to broke rules. Other eBay sellers may already found this information and could share with beginner. Anyway both posts were very helpful, and I appreciate your help.

"I prefer not to broke rules."

That is correct and none of the items you listed require you to register,

Business registration (includes GST or HST and import under the same number) is only required if your annual sales volume is $30,000 or greater.

As stated earlier, many sellers may find it advantageous to register with GST/HST if the sales volume is below $30,000 with a substantial percentage exported.  Registration with GST/HST allows Input Tax Credits.

Once again, regardless whether the business is registered or not, the net profit must be reported as business income on line 135 of the annual income tax return (that is what the government really cares about!).

"there is no need to register as a proprietorship with CRA or get a business number???"

That is correct as long as your annual worldwide sales are under $30,000

However, as stated earlier, there may be financial advantage in registering if a substantial percentage of your sales is exported.

To get Input Tax Credits (ITC) you must be registered.  ITC basically refund ALL the GST or HST you have paid on your purchases and business related expenses.

By not being registered, you do not need to collect or remit GST/HST but you also lose the ability to get ITCs.

Sellers who are not GST/HST registered CANNOT under any circumstances collect GST or PST from their buyer. It is highly illegal.