The 'Second' Tax
In addition to income tax, France levies 'social charges' (Prélèvements Sociaux) on most income. For investment income and capital gains, the standard rate is 17.2%. However, if you are covered by the health system of another EU country (or the UK), you may be exempt or qualify for a reduced rate of 7.5% (CSG/CRDS).
The US Credit Issue
The IRS has historically been inconsistent on whether CSG is a 'tax' or a 'social security contribution.' Current case law generally allows it as a Foreign Tax Credit. LSI keywords include 'Prélèvements Sociaux,' 'S1 Form,' and 'Income from Assets.'