How Does A Flexible Spending Account Work? Expert Tips

A flexible spending account (FSA) lets you set aside pre-tax dollars from your paycheck to pay for eligible medical expenses. You decide how much to contribute during open enrollment, and that money is deducted from your salary before taxes are taken out. This lowers your taxable income, which means you pay less in taxes and effectively save money on healthcare costs like copays, prescriptions, and certain medical supplies.

How Does a Flexible Spending Account Work at Its Core?

Think of an FSA as a special bank account for healthcare costs. Your employer sponsors the account. You choose an amount to contribute for the year, up to a limit set by the IRS. That amount is divided evenly across your paychecks and taken out before taxes.

When you have a medical expense, you use the funds in your FSA to pay for it. Most plans give you a debit card linked to the account. You can also pay out of pocket and submit a claim for reimbursement. The key advantage is that the money you spend never gets taxed.

One important detail: the money you put in an FSA is not the same as money in a savings account. You generally must use it within the plan year, or you risk losing it. This is known as the “use it or lose it” rule, though many plans now offer a grace period or allow a carryover amount.

What Can You Buy With an FSA?

The IRS defines what counts as an eligible medical expense. The list is broad, covering most things you would pay for out of pocket for medical care.

Common eligible expenses include:

• Doctor visits and specialist copays
• Prescription medications
• Dental work and orthodontia
• Vision exams, glasses, and contact lenses
• Medical equipment like crutches or blood pressure monitors
• Mental health counseling and therapy sessions
• Certain over-the-counter items like bandages and pain relievers

Some items require a letter of medical necessity from your doctor. This often applies to things like acupuncture, chiropractic care, or specialized equipment. If you are unsure whether a purchase qualifies, check with your FSA administrator before buying.

You cannot use FSA funds for cosmetic procedures, most cosmetic dental work, or health insurance premiums. Vitamins and supplements are generally not eligible unless a doctor prescribes them for a specific medical condition.

What Is the FSA Contribution Limit for 2025?

The IRS sets an annual limit on how much you can contribute to a healthcare FSA. For 2025, the limit is $3,300. This is an increase from the $3,200 limit in 2024.

If you are married, your spouse can also have their own FSA through their employer. Each of you can contribute up to the full limit to your own account. The limits apply per person, not per household.

Some employers offer a separate dependent care FSA for childcare expenses. That account has its own contribution limit of $5,000 per household for 2025. The rules for dependent care FSAs differ from healthcare FSAs, so keep them separate in your planning.

What Happens to Unused FSA Money at the End of the Year?

The traditional rule for FSAs is “use it or lose it.” Money you contribute but do not spend by the end of the plan year is forfeited to your employer. This rule still applies to many plans, but there are two important exceptions.

First, many employers offer a grace period. This gives you extra time — usually up to two and a half months after the plan year ends — to spend your remaining balance. If your plan year ends December 31, a grace period would let you use the funds until March 15 of the following year.

Second, many plans allow a carryover. You can roll over up to $640 from 2024 into 2025, and up to $660 from 2025 into 2026. The exact carryover amount changes each year based on IRS adjustments. Your employer chooses whether to offer a grace period, a carryover, or neither. You cannot have both.

If your plan offers neither option, you must spend your full balance by year-end. Check your plan documents carefully. Many people plan their spending early in the year to avoid losing money.

Can You Change Your FSA Contribution Mid-Year?

Generally, no. Once you set your contribution amount during open enrollment, it is locked for the entire plan year. This is different from a health savings account (HSA), where you can adjust contributions anytime.

There are exceptions. A qualifying life event lets you change your FSA election mid-year. Qualifying events include marriage, divorce, the birth or adoption of a child, a change in your spouse’s employment, or losing other health coverage. You typically have 30 to 60 days from the event to request a change.

If you leave your job, your FSA ends. You can use your remaining balance to pay for COBRA continuation coverage in some cases. Otherwise, you lose the unused funds. This is a significant risk to understand before committing a large amount to an FSA.

FSA vs. HSA: What Is the Difference?

People often confuse FSAs with health savings accounts. Both offer tax advantages, but they work differently.

An FSA is available through any employer that offers it. An HSA requires you to have a high-deductible health plan (HDHP). For 2025, an HDHP is defined as a plan with a deductible of at least $1,650 for individual coverage or $3,300 for family coverage.

Key differences:

• FSA money is generally use-it-or-lose-it. HSA money rolls over forever.
• FSAs are employer-owned. HSAs are individually owned, so you keep the account even if you change jobs.
• HSAs can be invested in mutual funds and grow tax-free. FSAs do not earn interest.
• Anyone with an HDHP can open an HSA. Only employees with access to an employer-sponsored FSA can use one.

If you have a choice between both, an HSA is usually the better long-term option because the money never expires. An FSA makes sense when you have predictable medical expenses and want immediate tax savings without meeting a deductible first.

What Are the Hidden Benefits of an FSA?

Most people focus on the tax savings, but there are other advantages worth noting.

Your full annual contribution is available on day one of the plan year. If you elect $3,300 for the year, you can use the entire amount in January, even though you have only contributed a fraction of it through payroll deductions so far. This is called “uniform coverage.” It can be a real help if you need expensive dental work or new glasses early in the year.

FSA funds also reduce your Social Security and Medicare taxes, not just your income tax. This is because the contribution is taken out before those payroll taxes are calculated. The savings are modest but real.

Some employers offer a limited-purpose FSA. This type of account can only be used for dental and vision expenses. It is designed for people who also have an HSA, because using a regular FSA would disqualify them from contributing to an HSA. If you have an HSA-compatible plan, ask your benefits team whether a limited FSA is available.

How Do You Avoid Losing Money in Your FSA?

Planning is the most effective way to avoid forfeiting your balance. Review your medical spending from the past year. Look at your prescription costs, doctor copays, and any planned procedures. Use that number as your contribution target.

If you find yourself with a surplus near year-end, several strategies can help you spend it:

• Schedule appointments you have been postponing, like a dental cleaning or eye exam.
• Buy replacement supplies like contact lenses, diabetic test strips, or first-aid items.
• Purchase a new pair of prescription glasses or sunglasses.
• Stock up on eligible over-the-counter medications like pain relievers or allergy medicine.
• Get a new blood pressure monitor or thermometer.

Do not buy things you do not need just to use the money. That defeats the purpose of saving. Instead, look ahead to the new year. If your plan offers a grace period or carryover, you may have more flexibility than you think.

What Happens to Your FSA When You Change Jobs?

An FSA does not travel with you. If you leave your job, you lose access to the account at the end of your employment. Any money you have not spent is forfeited to your employer.

You can use COBRA to continue your FSA coverage in some cases. This lets you keep contributing with after-tax dollars, but the practical benefit is limited. Most people simply plan to spend their balance before leaving.

If you are starting a new job with a different employer, you can enroll in their FSA during your new hire onboarding. You will set a new contribution amount for the remainder of that plan year. Be careful not to over-contribute if you have already used a significant portion of your previous FSA.