What are Social Security and Medicare (OASDI) taxes?

OASDI stands for Old Age, Survivor's, and Disability Insurance. OASDI is also known as Social Security. All employees are subject to OASDI and Medicare  witholding unless exempt by visa status and length of presence in the U.S. or by the student employee rules. The OASDI and Medicare rates, as well as the OASDI wage limit, are updated annually and posted on the Internal Revenue Service website. This tax includes an employee and an employer contribution.