NEW YORK — You may think that the chartreuse sweater you've chosen for your sister this Christmas is just what she wants. But what if it isn't?

Most holiday shoppers invest a lot of time and money in the "perfect" gift, but many fail to give any thought to what happens if it doesn't fit, the color is wrong or it's defective.

"You don't want your loved ones to have to go through a lot of hassle to exchange it or return it," said Lisa Lee Freeman, deputy editor of Consumer Reports magazine, based in Yonkers, N.Y. "So it should be part of your shopping homework this year to make sure the stores you're shopping have good return policies."

In an effort to fight fraud, many retailers have become stricter about enforcing return policies. Some will give store credit but not cash for returned goods. A number of big chains, including Best Buy, Circuit City and Sears, have begun charging "restocking fees" of up to 15 percent when big-ticket items such as cameras and TV sets are returned, usually if their boxes have been opened. Others, including Barnes & Noble, won't take back DVDs, CDs and video games that have been unwrapped.

Scott Krugman, spokesman for the National Retail Federation, said most stores are sensitive to the needs of consumers who are returning goods — especially at the holiday season — because they want to keep them as customers.

"Everyone is competing on price, so one way to differentiate yourself is customer service," Krugman said.

At the same time, he added, retailers "still have to protect themselves from return fraud," which can involve stolen or retagged merchandise as well as bogus receipts. It also can involve what's known as "renting," which is when a customer buys a dress or suit on a Friday, wears it to a big party on Saturday and tries to return it Sunday.

Return policies vary widely from retailer to retailer, so it's important that holiday shoppers educate themselves.

Most retailers post their return policies near their checkout counters. If they don't, consumers can ask the store's staff what the return policies are before they buy. Major retailers like J.C. Penney and Wal-Mart post their return policies on their Web sites, including the number of days after an item is purchased that it will be taken back.

Returning goods purchased online or can trigger other issues, Krugman noted. Who pays for shipping the return? Can returns or exchanges be made at a bricks-and-mortar site? Are there deadlines?

Freeman of Consumer Reports noted that it's harder to return things without a receipt. So she suggests buyers ask merchants for gift receipts to enclose with their presents. Purchasers also should keep their own receipts as backup, she added.

Gift receipts should ensure not only that a store takes an item back but also that the recipient gets credit for the actual purchase price and not a subsequent markdown price, Freeman said.