Reader: I just discovered that my employer failed to deduct my 2016 flexible spending account contributions from my paycheck. The employer had enrolled me, so I was still able to use the contributions (totaling $6,500 for the year) for medical and dependent-care expenses. Now — unsurprisingly — they have asked me to pay back the $6,500. I understand this is partially my fault for not following up, but I also don’t have that kind of cash lying around. Does my employer have any liability in this situation?

Karla: This is why it’s important for employees who open or renew an FSA to review their pay stubs at the start of the year — and for employers to remind them to do so. In the weeks between benefits enrollment season and the start of a plan year, it’s easy to lose track of deductions, especially in a paperless, direct-deposit payroll system.

Okay, lecture over. Mistakes were made. What you want to know is, who has to eat the cost?

Lawyer Terry Connerton, a benefits specialist who runs her own practice outside Pittsburgh, says that if an employer mistakenly deducts too much or too little from an employee’s paycheck for an FSA and discovers the mistake during the same plan year, the IRS has informally indicated that the employer can increase or reduce those deductions during that year to correct the error.

@Work Advice columnist Karla Miller. (Deb Lindsey/For the Washington Post)

But your employer found the mistake after the plan year ended. So who pays depends on what, if anything, your plan document and employee handbook say about resolving such errors. If there is no language explicitly stating that you have to repay the employer when it mistakenly failed to follow your instructions, then you might not be legally required to do so.

But you did, essentially, pay for health care and dependent care last year with money that wasn’t yours. Even if you technically have the legal right to take advantage of this error, it would be an act of good faith to agree to pay back the contributions if you intend to stay with this employer. And it would be good faith on your employer’s part to make that repayment as painless for you as possible by accepting it in installments, though doing so would pose a risk that you might leave before it recoups the entire amount and that the legal expense of pursuing you might outweigh any benefit it stands to gain, notes Toni Pilzner, an employment lawyer with McDonald Hopkins PLC in Detroit.

Bottom line: You should ask an employment benefits lawyer to review your plan document and handbook to determine what you’re legally on the hook for. Then, you’ll need to weigh your legal, ethical and financial concerns to decide whether it makes sense for you to challenge the repayment request or honor it.

Now if you’ll excuse me, I feel a sudden paranoid urge to review my benefits elections and pay stubs.

Ask Karla Miller about your work dramas and traumas by emailing wpmagazine@washpost.com. Read more @Work Advice columns.

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PRO TIP: Workers can use flexible spending accounts to pay for care for disabled adults who live with them and qualify as dependents. See IRS Publication 503, “Child and Dependent Care Expenses,” for more information.