Have you ever declined an already signed offer to take another one? If so, what's the way that you've handled it?

I just don't want to say to them that is for personal reasons because I'm pretty sure they would know it's about money .

(Signed offer but won't start in the position until June 1st.)

Signed or not, you should just talk to them and say you've been offered a position at X and feel it's a better fit for you.

You would be no doubt be on a pro a took period when you start anyway, this is used to A) make sure you're a good fit or sack you, and B) make sure they are a good fit for you or leave.

The earlier you walk, the better for everyone.

Once had been out of work for a while. Suddenly 3 offers at the same time. I'd already signed sort of an "intent to employ" document but didn't yet have my whole contract. Then got another offer, from the company I considered "first prize" for twice as much money (literally exactly double)

I emailed the first company an apology and explaination. They seemed a bit annoyed/disappointed but understood