What can I do in order to start earning work credits for Social Security ? Is filing a self-employment tax return from my income abroad enough ? I have dual citizenship and I live most of the year abroad (in Greece)
The only way that you can earn U.S. Social Security tax credits is by either earning wages that are subject to U.S. Social Security taxes, or by producing net earnings (NESE) from a trade or business subject to U.S. self-employment taxes. In 2020, you can earn 1 quarter of Social Security coverage (QC) for each $1410 of wages or NESE on which you pay Social Security or self-employment taxes, up to a maximum of 4 QCs. You cannot, however, voluntarily pay self-employment taxes on income that's not subject to U.S. self-employment taxes in an attempt to receive Social Security credits.
I'm not a tax expert, though, so I'm unable to give you specific tax advice. You may want to review the following IRS website regarding self-employment taxes.