You have to buy each year separately. They only sell and support the last 3 years back to 2014 now. Or if you have a simple return you can get the blank forms from the IRS and fill them out by hand for free. If you can't find them I have a list of them for all years.
You will have to mail in your return. And if you are doing more than 1 year, send each year in a separate envelope. Sometimes the IRS will just staple all the sheets together and miss a second return. Or you might want to go to an accountant or EA enrolled agent in person to help get you caught up.
But what is the rest of your question? Why do you need to do multiple years? Did you have income you didn't report? Or do you need to amend a prior year?
