And the one thing you must do regardless of whether or not you keep the gift.

Woman making purchase at boutique
Credit: Plush Studios/Bill Reitzel/Getty Images

You've made it through Chanukah and Christmas. All of your loved ones' bellies are full and happy. Your houseguests are starting to make their way back home. Pat yourself on the back for getting through another round of holidays.

But now comes the task of sorting through all of those wonderful and thoughtful gifts. And okay, maybe they aren't all that wonderful. It's possible that Santa or a family member missed the mark. Aunt Sue get you pajamas that are three sizes too small? Or did grandma send you a bedazzled kitten sweater that's just not your taste? Maybe Cousin Donna bought you a great gadget that you already have. That's okay. Returning unwanted gifts is an expected part of the holiday season, but there are some etiquette rules you should follow.

The most important rule is that no matter what the gift is, you must write a thank you note. Come on, you knew that already, right? The giver of the gift should never have to know that you hated it. Be gracious and kind. Always. And make Mama proud. Get that thank you note in the mail ASAP!

WATCH: How to Write a Thank You Note

Second, you shouldn't feel badly about returning something you were given if you don't like it or it doesn't fit. Keeping unwanted items that you won't use will just create a headache inducing clutter in your home. No one wants that. So return without guilt.

Now,how do you get rid of the items you do not want? There are a few options.

Without creating clutter, if you have the space, you can keep a few gifts that might be great for someone else in a closet or an out of the way cabinet. It's always a good idea to have an extra bottle or two of wine on hand for that last minute dinner party invite. Just be careful you don't re-gift to the person who gave you the gift originally. How embarrassing!

The easiest option, of course, is taking the item back to its store of origin. But that is only possible if the gift giver included the all important gift receipt. If he/she did not, well then you will have to decide if it's worth hurting someone's feelings to let on that you want to return it and need to know where the present was purchased.

If you are lucky enough to have a gift receipt, be sure to check the fine print. Each store has different policies regarding returns. Thankfully Fortune has a good breakdown for you to use as reference.

If returning the unwanted item is not an option, you can try to sell it online. The Mirror is reporting that nearly 80 million unwanted gifts will end up on eBay this year. But that is a lot of competition. You may not make as much as you'd want or expect.

The last option is perhaps the most honorable. You could donate the gift. Depending on the item, there are several charities that could benefit from the donation. Did you receive a dress or blouse that just isn't your style? What about making a donation to Dress for Success? Your unwanted gift could turn into a brand new opportunity for a woman in need.