Sounds like a job for a solicitor. Maybe you can get free legal aid to persue the employer. When this happened to a client of mine my client reported the employer to the Revenue. The Revenue carried out an audit on the employer, found nothing and then investigated my client seemingly in a huff as a small piece of information that my client provided in relation to the employer was incorrect. He also reported the employer to SIPTU to persue his CIF pension contributions. Again nothing was proven. This despite the fact that he was employed for 7 years with the employer - unknown to him he was never registered at the tax office. He then appointed a solicitor to enquire into the case and shortly thereafter he received his P60s for each year. The state agencies were absolutely no use to him.