3:05 PM
This might be largely pointless, and already argued a million times on this question, but I'd like to say it, because, golly, this comes up a lot. Also being in a chatroom does levy the etiquette restrictions of not posting redundant comments, as well.
I don't know how it is in your country or other countries but, at least in mine, your salary is a company secret. You are obliged by law (outlined in your contract) to NOT disclose your exact salary to anyone, period. Because of that, in my culture, asking someone what their salary figure is is uncouth at best if you are not close friends with said person.
Asking a complete stranger that is rude to the point of "Ah, I see - you are an uncultured swine that should be avoided. Thank you for pointing it out!".
A company asking an employee of another company what their salary figure is can, absolutely, be considered a form of corporate espionage or something alike.
If a "pay slip" is the piece of paper that outlines how much money you receive and what taxes are being taken out of your salary even under normal circumstances showing this to anyone who is not HR or absolutely authorised to see that information (read: almost no one, including your colleagues AND BOSS) is a grave offence and breaking of the law.
You can very easily with 100% chance of conviction be sued for that. Of course I'm not talking jail time, as much as disciplinary firing and a fine but I am unaware how to word "conviction" better for this case.
So, at least in my case, a company that I do not work for asking for my play slip is equivalent to, 100%, a form of corporate espionage, breaking of the law and rudeness to the point of being almost the same as insulting your mother to your face.
Depending on the company, you can report them and they possibly could face serious consequences. But it will be hard to prove and a lot of people would be too lazy to bother with that, so, in reality, nothing will happen, even over here.
Still, it's a clear sign for the line "Ah, thank you! Please, under no circumstances, NEVER contact me again." to be used.
I can not think of a situation where it would be even REMOTELY acceptable for a POTENTIAL employer to ask for your pay slip but maybe things are different in your country.
Thank you for coming to my TED talk! :D