Returning junk mail to the sender is an effective way of dealing with unsolicited mail that is difficult to stop, such as letters addressed 'To the Occupier'.
There are certain types of junk mail that are difficult to eliminate. In particular letters addressed 'To the Occupier' and leaflets from companies that ignore 'No Junk Mail' signs are pretty much unstoppable. If you don't want to put up with such unsolicited junk mail you got just one option: send it back. It's an informal way of stopping junk mail but it can be effective. And, if we would all send back all the junk mail we're not interested in we would soon have a lot less rubbish coming through our doors!
Most senders understand there's no point in continuing to target you with advertisments and leave you alone. It's a waste of their time and money and it's not in their interest to keep annoying you. Some organisations may need a couple of returns though; dealing with returned junk mail is often not much of a priority for bulk mailers.
It's true that there are also senders that won't even bother looking at returned junk mail. Unfortunately, there's little you can do to about this. It's not unlawful for an organisation to keep targeting you after you've returned their junk mail; only an 'official request' is legally binding (see Contact the sender). Returning junk mail to the sender is no more than an informal, polite request.
That said, returning junk mail is a lot easier and less time-consuming than sending letters of e-mails to individual junk mailers. It's also a good antidote for junk mail frustration. And, if we all returned all junk mail we're not interested in junk mailers would very quickly become a lot more careful sending out junk mail in the first place…
Junk mailers don't pay for items returned to them directly. However, indirectly there's a cost. The more junk mail Royal Mail has to return to senders, the more expensive its bulk mail service becomes. In other words, returning unwanted advertisements to senders affects the spectacular discounts junk mailers get from Royal Mail.
There's another cost for junk mailers; they need to spend resources on dealing with items that are returned to them. However, it can be argued that returning unwanted advertisements actually saves the industry money. By sending back unwanted junk mail you let them know that they're wasting time and money targeting you. Senders that respect your wishes and remove your details from their mailing lists save themselves money in the long run.
Senders do of course pay a (reduced) postage fee for any freepost envelopes that are returned to them - sometimes more than once. Do make use of any freepost envelope enclosed with junk mail!
If your business (or any other type of organisation) is getting lots of junk mail your only option is to send it all back to the senders. Organisations can't register with the Door-to-Door Opt-Out, Your Choice, and the Mailing Preference Service, nor can they stop junk mail by sending data protection notices to individual junk mailers. No opt-out scheme for junk mail send to organisations exists; there's nothing in the self-regulatory framework set up by the junk mail industry that can help organisations prevent unwanted mail; and there's no legislation that can help.
If you're getting lots of addressed junk mail and you want to make sure the senders get your message you should consider buying return to sender labels or a return to sender stamper. Incidentally, you can get them on this website :). A pad with 20 organic 'lick & stick' labels costs £1.25; the stamper costs £10.