I have a workers comp settlement coming to me but I owe the IRS back taxes can the take that settlement?

Yes, they can, and yes, they WILL!

What if a repayment plan is in place?

I am out on disability and owe back taxes to the IRS. I had a payment plan in place but being that I am out of work they have not been able to garnish a paycheck. Now they have taken every dime of my workers comp payment. Is that legal? Don't they have to leave you with something to survive on?

Yes, it is legal. You owe them back taxes, and that settlement is considered to be a windfall that is NOT essential to your everyday expenses.

You can appeal to the Tax Advocate to see if they can get some of the settlement, but I doubt it will do any good.