If you register your online venture as a business, then you will need to pay income tax. However, the types of taxes payable depend on the tax laws of the country in which you reside. This is where you will need to consult an accountant and learn about which tax laws apply to you and your online business.
You should also be able to claim all or a portion of your business expenses on tax. Your business expenses may include the cost of your computer, internet access, phone bills, home office stationery, home office lighting, home office heating, home office renovations, accountant fees, web hosting, advertising, computer software, etc. Your accountant should be able to list all the items that you may be eligible to claim on tax.