Supplemental Unemployment Benefits sound like a niche payroll concept until you encounter them in a layoff. SUB plans are how some employers cushion the financial hit of temporary layoffs by topping up state unemployment insurance benefits to something closer to the employee's normal take-home pay. The plans require careful structuring to qualify for favorable tax treatment, and they require coordination with state UI rules so they don't accidentally disqualify the employee from collecting underlying state benefits. When done right, SUB plans are a useful tool for managing temporary workforce reductions; when done wrong, they create payroll-tax exposure and can trip up state UI eligibility.
How a SUB Plan Actually Works A typical SUB plan does three things. It defines the eligibility criteria for receiving supplemental payments, usually tied to involuntary layoff for an economic reason rather than for cause. It defines the payment amount, often calculated to bring the employee's total income (state UI plus SUB) to a target percentage of prior wages, commonly 80 to 95 percent. And it defines the duration, often capped at a fixed number of weeks tied to length of service.
The supplemental payment runs through the employer's payroll system but is treated separately from regular wages for tax purposes. The employee remains formally separated from the employer during the layoff, which is what allows them to collect the underlying state UI benefit.
The IRS Rules That Make SUB Payments Tax-Advantaged Properly structured SUB payments are exempt from FICA (Social Security and Medicare ) under IRS rules established in Revenue Ruling 90-72 and refined in subsequent guidance. The exemption requires that the payment be tied to the receipt of state UI benefits, paid only during periods of involuntary unemployment, and not paid as a lump sum at separation (which would treat it as severance, subject to full FICA). The exemption is a meaningful saving (about 15.3 percent of the payment amount) but requires precise plan structure to claim.
Are SUB Payments Subject to Federal Income Tax? Yes. SUB payments are taxable as wages for federal income tax purposes, even though they're exempt from FICA. The employer withholds federal income tax based on the employee's W-4. State income tax treatment varies by state, with most states following the federal income-tax-yes, FICA-no treatment.
Where SUB Plans Show Up Most Often SUB plans are most common in industries with significant cyclical employment. The auto industry pioneered them in collective bargaining agreements in the 1950s and 1960s, and they remain standard in UAW contracts. Steel, aerospace, and some construction industries use them as well. Outside unionized settings, SUB plans appear at large manufacturers facing periodic shutdowns and at some employers that face seasonal demand swings. They're rare in office and professional environments, where layoffs tend to be permanent rather than temporary.
Setting Up a SUB Plan That Stays Compliant Five practices reduce SUB plan risk. Draft the plan document to meet the IRS Rev. Rul. 90-72 requirements, with explicit language tying payments to state UI receipt. Coordinate with state UI agencies in each state where employees may be laid off, since state rules on SUB plans vary and some states require notification or registration. Run SUB payments through payroll with the FICA exemption properly coded and federal income tax withheld. Document the layoff trigger and duration clearly so the SUB payments are demonstrably tied to involuntary unemployment. And review the plan periodically against current IRS guidance, since SUB plan rules have been refined repeatedly over the past 70 years. The IRS publishes detailed guidance on SUB plan tax treatment at irs.gov , and the Department of Labor publishes information on state UI program administration at dol.gov/agencies/eta .
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