Capital gains and income?

You will be taxed on 75k.    If you owned the stock more than a year, the 5k capital gain will qualify for the lower capital gains tax rate.    You would file a Schedule D and use the worksheet in the 1040 instructions to figure your tax.   If you go straight to the tax table, you'll overpay.

Since you asked in the Canadian section, I will give you the Canadian answer. Profits from selling securities are normally taxed as capital gains. In Canada, you only have to pay tax on 50% of the capital gain, not the full amount. Thus your taxable income for that year will be $72,500. 

at most,  75000, maybe less.

Your income increases by the amount of the profit.

You're right. It was a stupid question.

If you fill out the paperwork correctly, then you are taxed on only $75,000.  If you don't report the sale, then you are taxed on the full $100,000.  If you report the sale correctly, then your income is increased by only the amount of gain.  If you don't report the sale, then your income is increased by the whole amount of the sale.