The interest is really fair honestly. The only thing to keep in mind is that if you are on a payment plan, you can't start a new payment plan. You have to pay your future taxes in full every year, which is a little challenging while making the payments from last year at the same time. So as long as you're prepared next year to pay anything owed (for income this year), I'd opt for the IRS payment plan. Make sure you move quickly though as I found out the hard way that you'll still pay late penalties even if you set up the payment plan. Been in the same boat, and as much as I wanted to kick myself, it's best to just take the clear headed approach and move forward.