[lcnPylGDnU4H9OF]

> If they ask what you made before, you can say something like “I was underpaid at 80k, which is why I’m talking to you now.”

Agreed that it's best not to give false information but you can also respond with something like, "What is your budget for this position?"

It makes it obvious -- at least, it should -- that you know they're only asking, as patio11 puts it, as an attempt to get you to compromise your negotiating position.

Giving the number and calling it out as low isn't a bad idea, just offering another for those who would prefer not to give a number at all.