My employer paid me cash all year, and now I don't know what to do. Is it possible to become an independent contractor now to report 2015's income? Or is it too late?

A little more information: This is a nanny job, in the family's home. The parent was supposed to set me up for paying taxes but never did, and eventually I forgot about it. I know I should have known better... but anyway, now it's close to time to file for 2015 and I don't know what to do. The amount received from that family is about $20,000. I started another job in September and I will have a W2 from them.