Some people, when they return stuff, unintentionally give me a clear picture of their house. Two cases in point recently--two sets of sweats covered in dog and cat hair, and the sweatpants that had been through the wash were hairier than the rest. The green had a kind of roan or frosted look. The other case were camo-hunting pants coated in dog hair, with less near the waist band and a ton around the cuffs. In the camo-pants situation, I had a striking image of the person trying the pants on one leg at a time on avocado carpet with a good quarter inch thick of dog hair felted into the surface. Am I psychic? You decide.
Anyway, when you need to return clothes that don't fit, bear in mind:
If the merchant can't resell them because they've been washed or covered in dog/cat hair or sweated out/smell like perfume/smell like you've been in a cigar bar all night, you're basically asking them to eat the cost of the clothes because you made a mistake. They usually won't get a credit from the manufacturer. If the clothes are in good enough condition to hang back on the shelf, though, the merchant will be happy to accommodate you.
In marginal economic times, it doesn't take long before merchants have to decide whether to accommodate errors in size-choice (which we all make, and is a courtesy on their part) or to decide whether to keep their doors open. Returns are built into business plans, but it's not hard to see how increased returns, or just normal rates of return when the business is struggling due to greatly decreased sales, could kill a store that managed to survive up until this point.
I do understand that lots of people don't really care if the little clothing boutique dies or their local drug store closes ... but they better not complain that the only places still open are Fred Meyer and Walmart. And on the other side of the table--the best way to ensure you'll be able to return clothes that don't work for you is to take good care of them. More and more businesses are refusing to take back stuff that's been misused. They simply can't afford to take the hit anymore.
The exceptions, of course, are obvious manufacturing defects. The manufacturers make good on those.