Given the date how to return a costume sounds like a useful piece of advice. Or perhaps more importantly, whether you can return a costume. For it's not always true that we'll only get the one costume for Halloween, so what do we, should we, can we, do with any excess ones that we've got?
Well, perhaps the first and most important thing about holiday costume returns (and this applies year round of course, not just this week) is that yes, it is possible to return some costumes. However, it isn't possible to return all so the full details on what you can and cannot do are there at that link.
Probably the most important and obvious point to be made is that you cannot return things that you've worn and thus mussde up. Definitely no returns of underpants that have been worn for example (yes, even if it was the Superman costume and they were outside your tights).
Actually, a good rule of thumb (although do check, as I say, at the link for the full details) is that you can return really, properly, unused costumes: things that are still in the original packaging. Everything else, well, it depends.