startup of a small business - GST registration

My question is in regards to income tax exemption for a newly self-employed individual.
I currently work as a contractor doing software developement which I just started about 4 months ago. To set myself up as a contrator,
I started a small business as a sole proprietor. I can't confirm this, but I had heard that the few first months of a small business,
the income earned is exempt. Is this true? When I do my taxes for 2007, is the income I earned during the first few months or up
to a certain amount exempt from income tax?
Having said that, in starting my small business, I used an older registered business along with it's business number and name. I
only needed to change the address and, since my first business venture was computer related, I only had to change the nature of the business slightly.
I made no income from the older business. It was a side business which I put to the side and didn't do much with it.
If, from my new business, my initial earnings are exempt, does it still apply to me or since I used an older registered
business number and name? Is my 'new' small business not considered a 'new' business, but an old one?
david ingram replies

To give out income tax help, it always helps if I know what country you are in. Most of my questions come from the US but I think yours is from Canada.

There is no 'first few months' tax exemption for a new small business in either country.

Of course, the first $10,000 or so you earn from any business is tax free because of your personal exemption and a dedcution for 1/2 of the CPP you pay out as a self-employed person and all of the CPP and EI you pay as an employee.

CPP payments are essentlially 10% of everything over $4,000.  (this is not an exact figure because I do not know the figures for 2007 yet.) -  So, as a self employed person, if you had a profit of $10,000, there would not be any income tax, but you would owe $600 for CPP (Canada Pension plan).
You may be confusing the start up of a small business with GST rules.  You do NOT have to charge GST if you are doing or expect to do less than $30,000 Gross.  But 'IF' you know you are going to be doing over $30,000 gross business, you have to register and charge GST to Canadian Residents.  You do NOT need to charge GST if you are developing software for US clientele but even though you do not need to charge it, you have to register.  That is actually a benefit because when you file your GST 34 return, you will find that you get a refund of all the business GST you have paid in a year.