It's very simple. Go here: https://apps.irs.gov/app/picklist/list/priorFormPublication.html Then type in the form type you want. All the old years will show up. WARNING: Sometimes it is not best to file all old returns. If you are not sure or need help with your tax issues give us a call us at (888) 515-4829 or go to https://trp.tax/contact-us/ See our comprehensive tax help guide here: https://trp.tax/tax-help/