Expats moving to the United States will need a Social Security Number (SSN) before formally starting a job. This is used to report one's earnings to the government, and in this way it is similar to the National Insurance (NI) number in the UK.
Those residing but not working in the US are generally not eligible to apply for a Social Security Number.
Some businesses, such as credit companies and banks, will ask for a Social Security Number, but in most cases alternative identification methods are accepted. It isn't necessary to have a number in order to get a driver’s licence, register children for schools, or to get private health insurance.
All social security cards should be kept in a safe place, but it is possible to get a replacement if it is lost.
How to apply for a social security number and card
There are two ways to get a Social Security number depending on whether one is an immigrant or non-immigrant. Immigrants,or permanent residents, can apply in their home country before departing for the United States as part of the process of filing for an immigrant visa. Alternatively, a social security office can be visited in person on arrival in the US. Non-immigrants only have the latter option and can only apply once in the country.
There are offices in all towns and cities. Wait ten days after arriving in the US before applying at a social security office to allow time for the necessary documents to be available online. There is no charge for a social security number. The process takes about two weeks. When completed, applicants will receive a small card bearing their Social Security Number.