This one’s simple and straightforward, especially if you have a steady stream of clients. It’s the total of all invoices paid to your business within a specified period of time, as well as any other income.
Always set aside a percentage of every payment you receive for taxes. In general, 20% should cover it, but check with your governing tax agency to be sure.
This is the total of all purchases you made for your business in a specified period of time. Only money you spend on your business should fall into this category.