I second seeing if you can check out glassdoor for similar salaries in the field, get a feel for what is appropriate. After being at the same company for 10 years and getting the normal 2-4% increase, you may be significantly behind the curve salary wise. Depends on your industry and title. In software, job hopping routinely results in 30-50% salary bumps. Companies would kill to hire you at your current salary lol
Now if your industry isn't that ridiculous, you can still get a relatively good idea of how much you are worth.
I suggest keeping the info back. Companies like to fish for that information to have a starting point for negotiation. Give yourself the upper hand and negotiate for where you want to be, not defensively from where you are.
I'll give you a realworld example. My DH was looking for a new job because his current one was wearing on him. He got serious bites from the 2 places he was considering. The first one asked DH his current salary, and being trusting, he gave it to them. After me chewing him out, he didn't give the second company his current number even after they asked.
The first company came back at 5k over his original salary and refused to budge, since they knew that anything over that number was "good enough" and he didn't have much ammunition to negotiate further.
The second company offered straight out at 25k over his original salary, and he managed to eke out an additional 7k on top of that, because the company was blind to what his actual position was.
Guess which company now enjoys his services.
Companies will offer you what they think you are worth, but if they think they can get someone talented for cheaper, they will pounce on it. That's just good business sense--you want to pay people the least amount possible but still be competitive to attract talent. If someone comes along and doesn't realize how much they are worth, all companies can see is $$$ in their pockets.
edit: I would suggest answering the question with an answer to the question you *wish* they asked: "what is the salary range you are looking for?"
This is what my DH did with the second company. When they asked for his current salary, he sidestepped and said:
"Well, I'm looking for opportunities in the ABC-XYZ range, along with benefits. Thanks."
That gives them a number. The fact that it isnt your current number is not their concern.
edit again: or avoid the question all together. I would personally call and tell them that you would prefer to negotiate salary later in the interview process. If they are pushy, tell them that you can get a range of expected salary after some research. Then they might back down and allow that part to stay blank, or if they still want some number, go ahead and do said research and come back with that appropriate salary range that you think you are worth based on your experience, industry, etc.