From January through April this year I was a full-time employee at a company, but then I took a new job in May with a different company. For the first three months at the new job, I am considered a contractor, so I've been withholding my own income, Social Security and FICA taxes. After the beginning of August, I will be an employee and no longer have to do this. How do I pay the government the taxes I've been withholding on my own (for only these three months)? Do I need to pay now, or do I deal with this when I file for 2011 in 2012? What forms do I need? Thanks.