If you're not absolutely positive that Aunt Marge prefers Sony over Panasonic or if Cousin Ralph wants a digital camera instead of an iPod, it's more important than ever to check on return policies while shopping for high-tech gifts this season.

Many retailers, both online and in brick-and-mortar stores, have changed their policies on refunds and exchanges. Some are stricter because companies want to trim costs.

Some have changed because customers complained last year, others because of new technology. And some came as retailers expanded their Web offerings or partnered with Amazon.com (as Target, Office Depot and J&R; Music and Computer recently have).

Taking steps to make sure returns are legitimate - such as requiring receipts and refusing returns of certain items if they're opened - is a way for retailers to save money, said Ellen Tolley, spokeswoman for the National Retail Federation.

"Retailers aren't trying to be the bad guy or the Grinch to customers," she said. "They need to find a way of alleviating return fraud, which results in higher costs, and therefore higher prices to customers."

One of the strictest return policies can be found at struggling discount retailer Kmart, which is working to emerge from bankruptcy court. No refunds or exchanges are allowed without receipts, and even returns with receipts can be refused after 90 days. "You can attribute it to reining in costs," said company spokeswoman Abigail Jacobs.

Store managers are allowed to make exceptions in some cases, she added. "We don't want to anger our customers."

Thriving Wal-Mart, the world's top-selling retailer, is more relaxed.

Refunds and exchanges are permitted without receipts, and there's no time limit (though returns are still preferred within 90 days), said spokeswoman Sharon Weber. "We have a lot of confidence in our customers, in their ethics and integrity in bringing back items," she said. "That's what's brought us the success we've had - our focus on our customers."

As with many retailers, purchases from Wal-Mart's Web site are subject to slightly different policies than goods purchased in its stores.

Computers, electronics and media items such as DVDs bought from Walmart.com have time limits for returns (15 days for computers, 90 days for electronics and 45 days for other items).

At Circuit City, patron feedback persuaded the company to abandon a 15 percent restocking fee on certain electronics, said spokesman Jim Babb.

"Customers told us they didn't like" the fees, he said. Since the change, he said, "we've heard anecdotally from store managers that customers are pleased."

But other electronics sellers are keeping their restocking fees. They note certain items may need to be sold at a discount if they've been opened.

Target will impose the fees on camcorders, digital cameras and portable DVD players only if they are opened and clearly used, said company spokesman Doug Kline. Best Buy slaps the fee on any opened notebook computer, camcorder, digital camera or radar detector (unless it's defective).

This is the second holiday season Target has operated under a strict return policy that requires receipts and allows few exchanges without them. Before the change, Target launched new technology that helps customers who have misplaced receipts - it allows employees to look up transactions for customers who paid with credit card, debit card or check.

Target also began automatically printing gift receipts for most purchases.

Tips for returning holiday presents

Here are a few tips for returning holiday gifts:

Save receipts.

Read the return policy when making a purchase.

Ask for gift receipts wherever they're offered, and enclose them in gifts.

When ordering online, have items gift-wrapped and shipped directly to recipients so they'll have gift receipts.

Some stores have slightly different policies for purchases from their Web sites. Check on whether an item must be mailed back or whether it can be returned to a nearby store.

Computers and peripherals typically have a tighter return window than other electronics - usually 15 days.

Many retailers, including Best Buy, Circuit City, Radio Shack and Amazon.com, extend deadlines (excluding computers) until late January.

When it comes to CDs, DVDs, software and video games, most stores won't accept returns if they've been opened. Stores generally make exceptions if the item was defective, and then only an identical item can be substituted.

- Leigh Dyer