What is oasdi w/h? And why is it not appearing on my w2? Is this not a deduction?

[LindaA]

OASDI stands for old age, survivors, and disability insurance, otherwise known as Social Security. Social Security tax may be deducted from your income but it is not a deduction on your tax return. If you work for a state or local government agency and are covered only by your state or local pension, you don't pay Social Security taxes so you won't see an amount in box 4 of your W-2. There are other individuals who are exempt from paying Social Security tax as discussed here: Who Is Exempt from Paying Social Security Tax?