I think it's reasonable to ask what an interviewee expects to make, but not reasonable to ask what an interviewee makes now.
I had a job early in my career and they asked to see my W2 from my previous employer to validate that my previous job income answer was correct and finish onboarding.
Much better to instead have a second competing job offer in hand. Clearly that’s more competitive than your old job you’re leaving anyway.
As a freelancer who gets paid by the hour or by the job, I've never been in a position to negotiate salary directly, so I wonder how tenable it is to politely decline to answer questions about your current salary, given that it may give the potential employer more leverage against you.
I equate this to businesses (not you employer but places like the cable company) asking for your SSN: they may want it, but you are not always legally or morally obligated to provide them with it.
The Worknumber product from ADP (and it's equiv from Paychex) covers a vast range of white collar employees. Perhaps most.
Your new employer has a very good chance of seeing precisely what your current salary is down to the paycheck level going back years to even verify raises and title changes.
Replying with what you require to make to take the job seems like a much safer bet to me.
Might be wise to do before you interview.
You may not remember to opt back in to the "service" a certain number of months before you buy a car, for example. Then you're stuck either paying a higher interest rate because the lender sees you as riskier without a trusted method of verifying income, or you have to do a bunch of paperwork with the seller or finance company may or may not be willing to deal with.
It doesn’t have to be a lie. Between base salary and the value of benefits (and expected value of equity) you have a wide range of where you can answer what you’re paid, what your compensation is, what your “take home” is (what does that even mean if you’re W-2 and 1099?), et cetera.