my son worked for an under the table lawn service his employer now refuses to pay him for his work.What can I do?

your son is entitled to be paid regardless of whether this was under the table or not.  The only complication is that if your son had not been reporting the income as taxes for his 2011 return, this presents an issue with the IRS. But he is still entitled to be paid for his time.  If wages are only due for 2012, there is no problem tax wise at this point. You should  discuss this with an attorney to determine the best way to proceed