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You may have a budget all figured out that’s worked fine for years, but if you’re planning on retiring, you might want to consider how your spending will change once you’re out of the workplace.

While a Government Accountability Office analysis of 2013 data from the Bureau of Labor Statistics has found that retirees cut their spending once they leave the job, that doesn’t mean that what they spend their money on remains a constant.

And some of those changes can be costly.

The GAO analysis showed that people aged 50–64 who are still working spend, on average, $54,400 annually. Retirees aged 65–79, however, spend $12,500 less per year, for an average annual outlay of $41,900.

But while some costs go down, others rise—and retirees should be prepared to face those costs, lest they come in for some unpleasant surprises.

Retirees won’t be spending as much, generally, on transportation—no more commute—and can save a lot of money. Those aged 50–64 spend an average of $9,600 a year to get to and from work; by the time they’re retired and in their late sixties, those costs have dropped to $7,900.

But by the time they hit 80 and up, transport should be running more in the neighborhood of $3,600 a year.

Housing is pricey, no matter your age.

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But retirees can cut their costs by paying off an existing mortgage or by downsizing, among other strategies.

GAO stats indicate that while those aged 50–64 pay on average $17,000 a year for a place to live, retirees aged 65–70 have cut that down to an average of $13,700.

Food can run less for retirees, too, since they generally don’t spend as much on convenience foods and have more time (and often the inclination) to cook things from scratch. That 50–64 age group usually shells out an average of $7,700 annually, while folks aged 65–79 have shrunk that to $6,400.

Entertainment generally won’t go down by all that much, since retirees have more time on their hands to seek out activities to amuse themselves during all those leisure hours.

Read: 10 ways retirement is changing in the U.S.

On average, entertainment expenses only fall by about $300 to $2,000 a year—but, as retirees age, that can fall further, to $1,400. Still, if you’re an avid theatergoer, your entertainment costs might actually rise.

Since retirees no longer have to maintain a work wardrobe, their clothing costs often fall—from a preretirement average of $1,100 to a postretirement total of $800. They often spend less on durable goods, as well, since, as the GAO pointed out, “consumer durables purchased prior to retirement, such as furniture or household appliances, may continue working well into retirement and may not need to be replaced.”

But then there’s health care.

Workers aged 50–64 can spend an average of $3,900 a year on copays, prescriptions and other health care expenses—but for the 65–79 set, that increases to $5,000 on average.

The GAO said in its report, “The amount a retired household will spend on health care may fluctuate because health care costs can be variable and premiums and out-of-pocket medical costs may rise.”