This is such a thorny topic. But for some of us, writing is our job, and the income from it is what puts food on the table. So delays in being paid for accepted pieces can hit hard.
Usually, everything goes smoothly, and magazines pay when they say they will pay. Some magazines pay on acceptance - so shortly after the piece is accepted you should get your money. However do remember publishers may have a single end-of-month accounts run, so don't expect the money instantly. 'On acceptance' might actually mean 'end of the month in which the piece was accepted, or possibly end of the following month if it was accepted late in the month'.
Other magazines pay on publication. Again, 'on publication' might not mean 'the instant the magazine hits the shops', but could mean 'end of the month in which the magazine hits the shops, or possibly end of the following month depending on how up-to-date the accounts department are with their work'.
So don't hold your breath.
But sometimes it all goes horribly wrong. Maybe the magazine is putting a new accounts system in place. Or maybe there's been some other change of process, or a change in personnel. Or perhaps something's gone wrong with the actual payment process, and the magazine staff think they've paid you but the money hasn't arrived in your account.
Whatever, if enough time has passed and still no sign of payment, you're going to have to chase it up. I know we all get scared at the thought of contacting an editor and saying, um, excuse me, but can I have my money please? but that's what you must do. The editor will forward your email or letter on to the accounts department, and hopefully they will sort it out or get in touch. It might take several goes, and it's very frustrating (been there, done that, bought the t-shirt) but you are entitled to that money so you must keep at it.
So, how do you go about chasing payment? Well, to borrow from an article by April Aragam in the latest issue of The New Writer (in which, by the way, there is also an excellent article by Sally Quilford who asks Do Ghosts Kiss? - you're going to have to subscribe to the magazine to find out what that's all about!) try sending an email with the subject 'Payment Query' or similar, to the editor, worded something like this:
My story (title) was accepted/published on (date) and I was wondering if payment is on the way. Thank you for your time.
(your name and contact details)
Keep it short, keep it polite, keep it to the point. If you don't get an instant response, don't worry. The editor may be looking into it, or might have forwarded it to someone else to deal with, or maybe they are on holiday. If no response at all in a fortnight, send another mail asking politely if the editor has had chance to look into this yet.
What also happens sometimes, is that payment which should be sent automatically to your bank account gets rejected because not enough bank details were provided. Sadly, this seems to happen quite often with payments from overseas magazines. It's happened to me - I received an advice slip saying a magazine had paid me, but the money didn't reach my account though I kept checking. Eventually I had to query it, and then had to resend all my bank details. Then finally the payment arrived. So do check (especially if it's your first sale to a magazine) that you've provided all the details they need, and that the details are correct. Even if you're sure you sent the right details, send them again. And keep at it until you get that money.
It's frustrating, it's horrible to have to do, but selling stories is a business transaction. You kept up your side of the transaction, and provided the story. The magazine must keep up their side, and pay you. OK, things go wrong sometimes, but when they do, and you've chased payment, then the onus is on the magazine staff to sort it out and make sure you get paid. So don't let them forget about you!
I hope most blog readers will never have to refer to this advice. But unfortunately I know of a few who've been fighting for payment from different magazines for some time. Hopefully their payment issues will be sorted out soon.