Flexible spending accounts that set aside pre-tax wages for health care costs will have a cap in 2013 that workers need to keep in mind as they plan for next year.

Benefits-related open enrollment periods, the lone chance employees generally have each year to set up these accounts, are winding down for many companies. Starting in 2013, employees will be able to set aside no more than $2,500 in the accounts, which can be used to pay for a wide range of medical expenses not covered by insurance.

This limit doesn’t count the contributions a worker’s company may make to the account in addition to what the employee sets aside, said Jody L. Dietel, chief compliance officer with WageWorks Inc., a San Mateo, Calif., company that administers flexible spending accounts, or FSAs, for about 1.5 million people.

FSAs can lower a participant’s taxable income, but they come with the condition that the employee must spend the money before the end of the year or it is forfeited.

The government previously didn’t limit how much workers could set aside, but most companies capped contributions at around $5,000. The new limit was set as part of the health care overhaul, the massive law that aims to provide coverage for millions of uninsured people.

The limit may affect people who are planning for some big medical expenses in the coming year like a surgery or braces for children. FSAs also can be used to pay for things like alternative medicines like acupuncture and transportation expenses for a medical visit.

Employees of many companies also can set aside money in pre-tax accounts to cover the cost of child care or adult day care. The contribution limit for these dependent care savings accounts remains at $5,000. Dietel said that cap hasn’t changed for years.