You might find yourself trudging through a congested shopping center in the weeks after Christmas carrying bags full of pants that are too short and sweaters that aren’t your style. But the crowds and the heavy load might not be your biggest frustrations.

Before you embark on your post-holiday mall trip, read up on the rules and exceptions you might encounter when returning a gift you gave or received.

Some retailers have strict return timelines, so it’s wise to bring misguided gifts back sooner than later. But it can be tough to pinpoint the exact deadline.

Kmart is extending its return window, allowing shoppers to return until Jan. 31 items purchased between Nov. 1 and Dec. 24. But that applies only to items that typically have a 30-day return window. Some are excluded, including those sold by third-party sellers, floor care equipment, vacuums and major home appliances. And you can’t return Christmas seasonal items after Dec. 25. Don’t assume your product qualifies for a retailer’s extended holiday window. Look online to see which deadline fits your gift.

Showing up at the store with an unused gift isn’t always enough to receive a refund. You’ll likely need to come with additional proof. To avoid a wasted trip, arrive armed with a form of identification, your receipt or packing slip, and all packaging and parts of the product. Sometimes tags must be attached, too.

Help your gift recipients out by giving them the proof they’ll need. Most stores require a gift receipt and/or order number to process the return. Macy’s, for instance, sends back gifts returned by mail that are missing an invoice or gift receipt.

If you’re returning a gift that you purchased, you might receive a refund to your card, a store credit or cash.

For instance, Best Buy will reimburse you for most returned items the same way you paid. But if you paid more than $800 in cash or more than $250 by check or a debit card without a major credit card logo, you’ll be mailed a refund check within 10 business days.

You might really like your gift, but if it’s defective, you’ll need to return or exchange it.

The Better Business Bureau warns that warranties sometimes exempt stores from liability for damaged products. You’ll have to send those items directly to the manufacturer for a replacement.

Some products can’t be returned at all. At Wet Seal, lingerie, swimwear, jewelry and clearance purchases aren’t eligible for return or exchange. At Steve Madden, purchases of clearance items and jewelry are final. Tory Burch won’t accept anything that has been worn, altered or washed.

If you’re unsure of a retailer’s return policy, call customer service or look it up online before you make a trip to the store or post office in vain.

Courtney Jespersen is a staff writer at NerdWallet, a personal finance website. Email: courtney@nerdwallet.com. Twitter: @CourtneyNerd.

This article was written by NerdWallet and was originally published by USA Today.

The article Watch Out for These Return Policy Rules originally appeared on NerdWallet.