For nearly 30 years, employees who were eligible to use the accounts had to forfeit any unspent money at the end of the year. The new rule announced Thursday permits employers to let plan participants roll over up to $500.
The accounts, known as flexible spending accounts, allow employees to contribute money directly from their pay, before taxes are deducted. The accounts can then be used to pay certain medical expenses not covered by insurance.
Treasury said an estimated 14 million people use the accounts.