| I think your employer is trying to avoid the Nanny Tax! Your employer must issue you a W-2 to ensure compliance with the law. Clearly, your employer is trying to avoid paying the matching social security of 7.65% of your wages and possibly avoiding to pay for the workers compensation premium!
I am not sure that you can compel him or her to issue you one, as it may possibly result in your termination. But,perhaps a gentle persuasion might help. For example it might be in their best interest to stay in compliance with the law especially in case of an injury to you whilst working at their home! Your Workers compensation policy would ensure that you have medical coverage for your injury. | 
