tax on no profits?

You need an accountant to answer these questions.

I'm not one, but I'll answer as for what I know about tax law and practice ...

Yes. You can deduct what you've spent on advertising, even if it was advertising that didn't work. You pay tax on the net result after deducting expenses from income. Usually.

I think not, generally. But if it looks like you've been overspending on advertising by "buying it from a friend" or something that might be a "fiddle", the tax authorities might decide to investigate. It will depend on the circumstances. But in general, if you run your business badly and overspend on deductible items, you can still deduct them, as long as you have proper receipts/evidence for them, and so on.

Yes, that would normally be enough to "claim" it as an expense. It will show on either a credit-card statement or a PayPal account print-out? A tax office should normally accept either.

Okay so the decuction on biz expenses and such advertising is 100 percent right?

Not like 40c per dollar or something...i read sonerhing similar 25c per dollar for travelling cost somewhere...what about such stuffs as advertising?

I guess its full but then need a confirmation

[edit: after typing my answer I just realized you were in Canada, but I'm leaving it up for others who come across the thread]

In that exact scenario (assuming you're in the United States and you spent the $100 on a marketing campaign), then no, you wouldn't be responsible for paying taxes on that $100. Media costs are a legitimate deduction, and if you roll your revenue back into marketing then technically you aren't profitable by the IRS's definition.

Be careful though - the IRS does consider some expenses YOU might define as "marketing" ineligible for deductions. If you send out samples or gift bags, you might consider that marketing but you're only legally allowed to deduct up to $25 per gift. Meaning if you're give 100 people $100 worth of products as part of a promotion, you can't write off $10,000 - you can only write off $2,500.

"Sales Activities" have limits, media does not. Keep this in mind. If you print a banner and stick it on your car, you can deduct the cost of your banner but not the cost of your car or your mileage while you're driving it around (there are separate allowances for mileage during business use, just don't throw it in the marketing bin - they will nail you).

Disclaimer: I'm just talking about the Federal level btw. Individual states have different rules on what's allowed and what's not, so you'll need to talk to an accountant in your state.

It's technically taxable as soon as you recieve it.

The reinvestment / expenditure is to be considered separate and therefore you should have the $100 income in your books (to be taxed) and the $100 as an expense.

In and outs.

Most money spent on your business can be used as a text brake. Just remember to not blur the line because this can get you in trouble. If you have even have doubt call your account to make sure.