Hello, I need help filling out nil provisional tax returns(IRP6s) for a sole proprietor.

I assume you leave the amounts nil but the returns I'm doing are for assessment years dating back to 2010. How will this affect the historic information section? Also is it necessary to put an estimated taxable amount, as the company was closed for those periods? Also how many returns will I have to do for each year of assessment? I know its usually 2 returns but I don't know the taxable income for the company and it is a nil return, so can't I just submit 1.