(UNITED STATES) — International students who move from OPT or STEM OPT to H-1B status in the same calendar year must split their wages by status period when reviewing Social Security and Medicare withholding, because the tax treatment can change on the exact date the new status takes effect.

Payroll should not treat the entire year as a single category, even if the worker stayed with the same employer. FICA treatment depends on visa status, tax residency, work authorization and the wage period tied to the services performed.

FICA taxes are Social Security and Medicare taxes withheld from wages. Many workers see those deductions on every paycheck, but some F-1 students working under authorized student employment, including OPT and STEM OPT, may have FICA-exempt wages if they are nonresident aliens for tax purposes.

That exemption generally ends once the worker changes to H-1B status. The IRS has specifically said the FICA tax exemption becomes inapplicable when a payee changes to H-1B nonimmigrant status, and that an employer must start withholding FICA taxes on the effective date of the status change.

A common example runs from January through September on STEM OPT, then from October through December on H-1B. In those cases, wages from the first period may qualify for exemption, while wages from the second period generally do not.

The same employer can create the confusion. A worker may perform the same job all year, receive one W-2 and stay on the same payroll, yet the tax treatment still turns on wage period rather than employer identity or calendar year totals.

That is why two broad payroll shortcuts can both be wrong: “You were H-1B this year, so all wages are subject to FICA,” or “You started the year on OPT, so all wages are exempt.” Both approaches can produce the wrong result.

Pre-H-1B wages may qualify for exemption if several conditions are met. The worker must be in valid F-1 status, have valid OPT or STEM OPT authorization, hold employment connected to the F-1 program, remain a nonresident alien for tax purposes, and receive wages for services performed before the H-1B status became effective.

If those conditions are satisfied, FICA withholding on OPT or STEM OPT wages before the H-1B start date may have been improper. That issue often appears after an employer withholds Social Security and Medicare taxes from the first paycheck of the year and never adjusts when the employee is still in F-1 student status.

Post-H-1B wages follow a different rule. Once H-1B status begins, the F-1 student exemption generally no longer applies, and wages paid for services after the effective date are generally subject to Social Security and Medicare taxes.

For many cap-subject workers, that dividing line is October 1. Not every case is identical, and workers should confirm the exact date through the approval notice and immigration records rather than assume every H-1B change starts on the same day.

An employee who worked on STEM OPT from January 1 through September 30 and changed to H-1B on October 1 illustrates the split. If that employee remained a nonresident alien during the STEM OPT period and the work was properly authorized, wages from January through September may be exempt, while wages from October 1 onward are generally H-1B wages subject to withholding.

The reverse errors also matter. If payroll withheld FICA for the full year, the worker should separate wages before and after the H-1B effective date and seek a refund only for the pre-H-1B OPT or STEM OPT period if eligible.

If payroll failed to withhold FICA after H-1B began, the issue shifts from refund to correction. The worker should notify payroll or HR, because the employer may need to correct withholding and reporting for wages paid after H-1B status took effect.

Tax residency can change the result even before H-1B starts. OPT and STEM OPT wages are not automatically exempt in every case, because the worker must still be a nonresident alien for tax purposes during that period.

Students who have been in the United States for more than five calendar years face a separate check. After the five-year F-1 exempt-individual period, the Substantial Presence Test may apply, and if the student becomes a resident alien, the FICA exemption may no longer apply even while the person remains in F-1 status.

That makes two questions necessary for the OPT portion of the year: whether the worker had valid F-1 or OPT authorization, and whether the worker still qualified as a nonresident alien. One without the other does not settle the payroll issue.

Income tax withholding does not answer the FICA question. A worker may be exempt from Social Security and Medicare tax during the OPT period and still face federal income tax withholding on wages.

The employee may need to file Form 1040-NR, Form 1040, or a dual-status return depending on tax residency for income tax purposes. Federal income tax withholding and FICA withholding operate as separate systems, so one cannot be used as proof of the other.

Workers who believe FICA was wrongly withheld during OPT or STEM OPT should first ask the employer for a refund. The supporting records include the I-20 showing OPT or STEM OPT authorization, the Employment Authorization Document, the I-94 record, passport and visa records if available, pay stubs showing FICA withholding, the W-2, an explanation of nonresident alien status, and a payroll period breakdown showing wages before the H-1B effective date.

If the employer refuses or does not refund the full amount, the worker may need to use Form 843 with supporting documentation. That route is the next step after asking the employer, not the first one.

The date on the paycheck may not tell the whole story. Payroll may need to identify the service period covered by each paycheck, because wages earned before the status change can fall into a different FICA category than wages earned after it.

That puts the exact H-1B effective date at the center of the review. Workers are told to check the Form I-797 approval notice, the change-of-status effective date, the H-1B start date in employer records, payroll period dates, paycheck dates and service periods, and whether wages were earned before or after the change.

The practical review is detailed but narrow. Workers who changed from OPT or STEM OPT to H-1B in the same year should compare the exact H-1B effective date with the OPT or STEM OPT end date, identify pay periods before and after that date, check whether FICA was withheld during the OPT period, and confirm whether withholding started after H-1B began.

They also need to review whether they remained a nonresident alien during the OPT or STEM OPT period, whether they crossed the five-calendar-year F-1 limit, whether the employer issued one W-2 or a corrected form, and whether a payroll refund is still possible before turning to Form 843.

Several recurring mistakes appear. One is asking for a refund of all FICA withheld during the year without separating wage periods. Another is assuming OPT wages are always exempt even after the worker becomes a resident alien for tax purposes.

Others include assuming H-1B wages stay exempt because the worker previously held F-1 status, treating federal income tax withholding and FICA withholding as the same issue, ignoring October 1 or the actual H-1B effective date, filing Form 843 before requesting an employer refund, failing to keep payroll emails and documentation, not checking whether a W-2c is needed, and forgetting that income tax filing status must be reviewed separately.

The central point is straightforward: FICA treatment should follow status and wage period, not the worker’s job title, employer, or year-end total. Eligible pre-H-1B wages may be exempt if the worker was a nonresident alien with proper F-1 employment authorization, while post-H-1B wages are generally subject to Social Security and Medicare taxes.

That leaves payroll records, pay stubs, W-2s, immigration dates and tax residency as the documents that matter most. In an OPT-to-H-1B year, the dividing line is not the calendar year itself, but the exact day H-1B status begins.