WASHINGTON (AP) — Want more time off work to hang out at the beach? Need a little cash and have vacation days to spare?

Some companies allow their employees to buy and sell vacation time, a perk that gives workers more flexibility in managing their time off.

The novel approach might help employees buy some extra days off to take the trip of a lifetime or spend more time with a newborn. Co-workers could sell off unused days to get some extra money.

"When times are a little tight, this benefit really doesn't cost a lot of extra money to employers to provide," said Julie Stich, research director for the International Foundation of Employee Benefit Plans.

A soon-to-be released survey by the Society for Human Resource Management found that 9 percent of employers allowed workers to cash out unused vacation time. Five percent let employees purchase additional vacation days through a payroll deduction. An additional 7 percent allowed employees to donate vacation time to a general pool that can be used by other workers.

The approach is even more popular with employers that have "paid time off" or PTO plans that combine vacation time, sick leave and personal days into one comprehensive plan. About 52 percent of employers reported offering such plans. Of those, 19 percent offered a cash-out option and 15 percent offered a donation program. One percent give their workers unlimited time off.

The cost is usually one week's salary, prorated over the course of the year. Employees often have to decide whether to participate during an annual fall enrollment process and it becomes part of their benefits for the upcoming year.

Nora Kouba, who manages company cars at construction materials giant USG Corp. in Chicago, said she used to buy an extra week off to care for her kids or take long summer vacations with the family. But these days, she tends to sell her excess vacation time.

USG allows all 9,000 of its employees worldwide to buy or sell up to a week of vacation time each year.

A flexible vacation policy has been in place about for about 15 years at Kimberly Clark Corp., based in Irving, Texas. The company allows employees to purchase up to five extra vacation days each year.