The short answer
OASDI on a pay stub is Social Security tax. In 2026 it's 6.2% of your wages up to the Social Security wage base of $184,500, and your employer pays another 6.2% on top. MED is Medicare tax: 1.45% of every dollar of wages, with no cap, plus an extra 0.9% once your wages pass $200,000 for the year. Together, OASDI and Medicare are FICA, 7.65% for most workers. FIT is federal income tax withholding, which depends on your Form W-4 rather than a fixed rate.
Common pay stub tax codes
| Code on your stub | What it is | 2026 rate |
|---|---|---|
| OASDI, SS, Soc Sec, FICA-SS, Fed OASDI/EE | Social Security tax (Old-Age, Survivors and Disability Insurance), your share | 6.2% of wages up to $184,500 (2025: $176,100) |
| MED, MEDI, Medicare, FICA-Med, Fed MED/EE | Medicare tax (hospital insurance), your share | 1.45% of all wages, plus 0.9% on wages over $200,000 in the year |
| FIT, FITW, FWT, FWH, Fed W/H, Fed Inc Tax | Federal income tax withholding | No flat rate: based on your pay and your Form W-4 |
| Fed MWT, Fed MWT/EE | Not a standard code. On stubs that also show separate OASDI and MED lines, it's usually federal income tax withholding | See below how to tell |
| SIT, SWT, St W/H, or a state code like CA ST | State income tax withholding | Set by your state; none in states without an income tax |
| SDI, CASDI, DI | State disability insurance, in the few states that have it (such as California) | Set by the state |
| Local, LIT, City, School | City, county or school district income tax | Set locally |
| EE / ER | Employee share (taken from your pay) / employer share (paid by the company, not taken from you) | — |
Payroll companies each use their own abbreviations, so the same tax can show up under different names. The "EE" at the end of a code like Fed OASDI/EE or Fed MED/EE just means it's the employee's share.
OASDI: Social Security tax
OASDI stands for Old-Age, Survivors and Disability Insurance, the official name of Social Security. The tax funds retirement, survivor and disability benefits. You and your employer each pay 6.2%, and self-employed people pay both halves, 12.4%. It stops once your wages for the year reach the wage base set by the Social Security Administration: $176,100 for 2025 and $184,500 for 2026. The most an employee can pay for 2026 is 6.2% × $184,500 = $11,439.
If you work two jobs, each employer withholds OASDI until its wages reach the cap, so you can end up paying too much. The excess is credited back when you file your Form 1040.
MED: Medicare tax
The Medicare tax rate is 1.45% for employees and 1.45% for employers, on all wages. Once your wages from one employer pass $200,000 in a calendar year, the employer must also withhold the 0.9% Additional Medicare Tax on the rest, with no employer match. On your return the 0.9% actually applies above $200,000 for single filers, $250,000 married filing jointly and $125,000 married filing separately, so the withholding may not match exactly.
FIT and FWT: federal income tax
FIT (federal income tax) or FWT (federal withholding tax) is your income tax, paid in advance. The amount depends on your gross pay, pre-tax deductions and the filing status, dependents and adjustments on your Form W-4. Unlike OASDI and Medicare there's no single rate. If too little is withheld you'll owe when you file; see why you might owe taxes.
What is Fed MWT on my paycheck?
There's no IRS code called MWT; it's a label some payroll systems use. To tell what any line is, divide it by your gross pay for the period. If it's 6.2% it's Social Security, if it's 1.45% it's Medicare, and if it's any other amount that changes with your W-4, it's federal income tax withholding. When in doubt, ask your payroll department.
Check your own stub
Say you earn $2,000 every two weeks. OASDI should be 6.2% × $2,000 = $124.00 and Medicare 1.45% × $2,000 = $29.00, or $153.00 of FICA in all. Some pre-tax benefits, like health insurance through an employer plan, can make the wages these taxes apply to smaller than your gross pay, so your lines may be a little lower. The FICA tax calculator does this for a whole year, and the take-home pay calculator adds income tax.
Self-employed?
Without an employer, you pay both halves as self-employment tax: 12.4% for Social Security and 2.9% for Medicare, 15.3% in all, on 92.35% of your net profit. See the self-employment tax calculator.
Sources
- SSA: Contribution and benefit base – $176,100 (2025) and $184,500 (2026); 6.2%/1.45% and 12.4%/2.9%
- IRS Topic 751, Social Security and Medicare withholding rates – employee and employer rates
- IRS Publication 15 (2026) – 2026 wage base, no Medicare wage limit
- IRS Topic 560, Additional Medicare Tax – 0.9%, thresholds, $200,000 withholding rule, no employer match
- 2026 Form W-4 – what sets income tax withholding
General information for tax years 2025 and 2026, not tax advice. Figures come from the IRS, SSA and state sources listed above.