You concentrate on smiling as you hold up the hideous gift you have just unwrapped.

It's the thought that counts, they say, but you're not quite sure what the person who gave you this gift was thinking.

Luckily, you've read this article.

Because if you're going to try to return that gift to the store it came from, it will help to have a working knowledge of Australian Consumer Law.

As lawyer Katie Miller told ABC Radio Melbourne's Lindy Burns, shops over the Christmas and New Year period are often staffed by summer casuals who "may not be completely au fait with the rules that relate to returns".

"It's the Australian Consumer Law, this is actually a federal law and the shops are bound by these things."

So what are the rules?

"The first thing to know," Ms Miller said, "is that the rules are no different at Christmas time compared to any other time of the year."

That means you can always return something if it's faulty or doesn't do what it's meant to.

"So if it's a phone that doesn't make phone calls; if it's a TV that doesn't switch on," Ms Miller said.

You can also return something if it doesn't match the advertised description.

"This I think particularly applies if you're buying things online," Ms Miller said.

For example, you might have bought a piece of furniture based on its advertised dimensions, only to find it doesn't fit in the spot you'd carefully measured.

"That means that that the goods don't match the advertised description and you can take it back for that reason."

Finally, if you get to New Year's Day and the dolphin lamp you got for Christmas has stopped working, you can return it.

The law says you can return an item that doesn't last a reasonable amount of time, but Ms Miller noted "that really depends on what you're buying".

"What's a reasonable time for a fidget spinner will be very different to what's a reasonable time for a smartphone."

Nothing's wrong with it, I just hate it

Ms Miller's recommendation is that you "act promptly".

"The store's going to want to resell it, so keep it in its original packaging and get back to them as quickly as possible," she said.

"Maybe not Boxing Day, because they've got other things on their mind, but try to act promptly and it is a good idea to have your receipt."

Things get harder if you don't have a receipt, but even if you do there's no obligation on the store to take back an item simply because you don't like it.