Working in a foreign country, paying into social security.

Social Security does not have voluntary payments, and you are limited to four quarters of social security credit in any calendar year.

He is not required to pay into SS but he may choose to do so. Use Schedule SE with the US tax return to report the SS wages and pay the tax. He will have to pay both the employee and employer portions (i.e. the 15.3%.) Once he makes this choice, he must continue to make the annual payment for as long as he is employed by this company.

Lanny K. Williams, C.P.A. Nawarat, Williams & Co., Ltd. Income Tax Services for Expatriate Americans

Some countries' tax treaties with the U.S. provide for credit with the U.S. system if he's paying into a foreign equivalent system. You need to check the treaty of the country he's in (if there is one).

The Totalization Agreements (tax treaties) with other countries allow for receiving credit for work performed in a foreign country where you had to pay into that country's equivalent social security system. One can use those work credits to qualify for US benefits if one does not have enough work credits in the US. However, one does not receive any contribution credits for the time worked in a foreign country. In other words, you get the quarters worked but your foreign earnings stay with the foreign country. Your US benefit is based on contributions to the SSA system and quarters of work including foreign service. Obviously, a reduced benefit... but at least some benefit.

As the earnings stay in the foreign country, it is also possible to qualify for a social security benefit from the foreign country using the same period of time worked in that country.

Information on Totalization Agreements is at: