Use this free IRS penalty and interest calculator to estimate how much you owe in failure-to-file penalties, failure-to-pay penalties, and accrued interest on unpaid taxes. The failure-to-file penalty is 5% per month (max 25%), failure-to-pay is 0.5% per month (max 25%), and interest accrues at approximately 8% annually compounded daily. See how much you could save with penalty abatement options including First-Time Abatement and reasonable cause relief. Neil Jesani Tax Resolution provides expert penalty abatement representation from 70+ tax professionals. Call (800) 758-3255 for a free penalty review.