I worked for an American company in Luxembourg for 11 years from 1987 to 1998 and qualify for Luxembourg national pension (social security) when I turn 65. I paid in to both US and Luxembourg social security from 1987 to 1991, then just Luxembourg from 1992 to 1998 after the totalization agreement with Luxembourg was signed. I am looking to start collecting my Luxembourg social security when I turn 65, but will probably defer my US social security until I turn 70. Can I apply for the Luxembourg social security separately from the US social security? I have been told told by some sources that I need to apply via the US Social Security administration, and they will forward the request to the Luxembourg social security administration. Will the Luxembourg social security reduce my US social security?
U.S. Social Security regulations wouldn't force you to apply for your U.S. benefits at the same time that you apply for benefits from Luxembourg, but I'm not an expert of Luxembourg's Social Security program so I don't know what their regulations might require. You could start the process of applying for benefits from Luxembourg at a U.S. Social Security office, but it's not required that you do so. You're free to instead file directly with Luxembourg if you prefer.
If you qualify for benefits from the Luxembourg program only because of the totalization agreement, then your Luxembourg pension wouldn't affect your U.S. Social Security benefits. But, if you would qualify for the Luxembourg pension even if there was no agreement, or in other words if Luxembourg doesn't need to use your U.S. credits to make you eligible for benefits from their program, then receipt of the Luxembourg pension could cause your U.S. Social Security retirement benefit rate to be reduced unless you meet an exception to the Windfall Elimination Provision (WEP). The most common exception is for people with 30 or more years of substantial earnings under the U.S. Social Security system. The amount of earnings needed to be defined as substantial varies from year to year, and the amounts can be found on page 2 of the following Social Security publication: https://www.ssa.gov/pubs/EN-05-10045.pdf.
By the way, our software (https://maximizemysocialsecurity.com/purchase) is programmed to handle cases involving WEP, so you may want to use it to help with your Social Security planning.