Returning a gift? Beware: More than a few major stores have altered their previously generous open-ended return policies this year.

Millions of Americans are heading back to the stores this week to cash in on sales and return those gifts that just didn’t work out quite right. About 10 percent of all holiday merchandise winds up coming back, according to the National Retail Federation. And despite the financial hit – about $60 billion dollars – most stores offer special extended holiday return periods.

However, a few prominent retailers have shortened their return policies this year, according to an annual survey by ConsumerWorld.org.

Macy's now requires all returns in one year

Kohl's has a new deadline for "premium electronics" of January 31

Costco reduced its return period for major appliances to 90 days

Tightening Up the Returns

“It’s surprising to me that these three big retailers put an end to their unlimited return policy for some or all categories of items,” said Edgar Dworsky, founder of ConsumerWorld.org. “How strict or lenient return policies are seems to be cyclical. We seem to be in a period of some tightening.”

Drones were a popular gift item this year. If you got one and you want to take it back, you’d better get going. The return period for drones is just 14 days at Target, 15 days at Walmart and 30 days at Toys “R” Us.

Shorter return periods are most likely a response to the serious and growing problem of return fraud. Retailers estimated that 3.5 percent of their holiday returns last year were fraudulent, according to the NRF’s 2015 Return Fraud Survey. That fraud cost retailers $2.2 billion, up from approximately $1.9 billion in 2014.

Even so, a few stores made their return rules more lenient this year. Two noteworthy changes:

Sears started its holiday returns policy one week earlier (November 1) and now allows returns one week later (January 30)

Toys"R"Us increased the return period for computer hardware from 15 to 30 days

The Consumer World report noted that Toys “R” Us has a generous but “secret” holiday return policy that is not disclosed on its website, posted at stores checked, or known by store employees asked. That policy is: Most things – other than select electronics, such as video game hardware, cameras and computers – purchased on or after September 1 can be returned until January 28.

“I simply can't understand why Toys "R" Us, which has one of the liberal holiday return policies in the industry, keeps it a secret,” Dworsky told NBC News.

When contacted about this, Toys “R” Us sent NBC News a link to a freshly released statement about post-Christmas sales. The news release is posted on the company’s corporate site. The policy still does not appear on the return policy page where consumers would go.

Better Have a Receipt

Do yourself a favor and bring along the receipt or a gift receipt. Some retailers won’t accept a return without a receipt. Others will only give you a store credit for the lowest price that item sold for recently, not what the gift-giver paid for it.

"Receipts are critical,” said Consumer Reports money editor Lauren Lyons Cole. “Merchants in the past have been fairly generous in taking back goods without a store or gift receipt, offering shoppers who can’t produce documentation at least store credit for the lowest price the item sold for. Though it’s rare for companies to have a blunt no-receipt, no-return rule, the lack of receipt puts you on shaky ground, especially for cash purchases because there's no way to look up the purchase."

Don’t be surprised if you’re asked to show identification – your driver’s license or other government-issued ID – even if you have the receipt. Some big chains now use computerized systems to detect return abuse. Consumer Reports say they use your ID to track your return history, including frequency, dollar amount and time between returns.

For example, Walmart limits customers to three returns without a receipt within a 45 day period.

Consumer Reports just published a Guide to Returning Gifts that includes a list of the “Best in the Business” and stores with strict policies.

It’s important to check the policy for any gifts purchased online. Some merchants cover the cost of the return shipping; others make you pay for it. Some stores with walk-in locations will let you return merchandise in person.

It’s important to remember that returns and exchanges are a courtesy. Except for damaged merchandise, a store is not required to take something back. And while many states require that return policy to be posted, the store gets to set the rules.

“When you get in that long return line, check the store's policy while you're waiting,” Consumer World’s Dworsky told NBC News. “If you are asking for something outside the rules, recognize that and adjust your attitude accordingly. You can’t demand something you're not entitled to. You can only ask politely for an accommodation.”

Herb Weisbaum is The ConsumerMan. Follow him on Facebook and Twitter or visit The ConsumerMan website.