Nellie

I was self employed from 1983 to 2015 and completed my self assessment form each year. When I retired in 2015 I carried on filling out the form because I was in receipt of pensions and savings interest and no-one told me I could stop. On discovering this year that I could request removal from SA I filled out the online form but it tells me I am over the 4 year period for submission. What does that mean? What can I do?