The IRS runs the numbers. Now you can too.
Penalties stack. Interest compounds every day. The collection clock stops and starts. These guides show the statute, the formula, and worked examples so you know what you actually owe and why.
Pick the number you are trying to understand
Most-used calculations
Filing Late and Paying Late: The IRC 6651(c)(1) Overlap Math
When failure-to-file and failure-to-pay penalties run in the same month, IRC 6651(c)(1) offsets them. See the 5% monthly combined rate and the 47.5% maximum.
open guide ->InterestHow IRS Interest Compounds Daily Under IRC 6622
How the IRS calculates interest on unpaid tax: the 6621 rate, daily compounding under IRC 6622, quarterly rate changes, and a worked 18-month example.
open guide ->CSEDHow to Calculate a Collection Statute Expiration Date, Step by Step
How to compute the IRS collection statute expiration date: find the assessment date, add 10 years under IRC 6502, then add tolling days the way the IRM does.
open guide ->OICThe Reasonable Collection Potential Formula for an Offer in Compromise
How the IRS computes reasonable collection potential for an offer in compromise: equity plus future income, with a full worked example and the 20% rule.
open guide ->TFRPComputing the Trust Fund Recovery Penalty Amount from Form 941
How the IRS computes the trust fund recovery penalty: which Form 941 lines are trust fund, how deposits are applied, and a worked quarter under IRC 6672.
open guide ->InterestIRS Underpayment Interest Rates by Quarter, 2022 Through 2026
Every IRS underpayment and overpayment interest rate by quarter from 2022 through Q4 2026, how each rate is set under IRC 6621, and how to apply them.
open guide ->Calculators
A free public calculator, plus practice tools for the firm.
Background articles
Plain-language overviews of how IRS collection works.
- Offer in Compromise Explained
- IRS Installment Agreement Guide
- IRS Fresh Start Program Explained
- Currently Not Collectible Status
- IRS Wage Garnishment: How to Stop It
- IRS Bank Levy Release
- Tax Lien vs. Tax Levy
- IRS Penalty Abatement Explained
- IRS Audit: What to Expect
- IRS Appeals: How to Challenge a Decision
- Unfiled Tax Returns: What Happens
- Substitute for Return (SFR)
- Statute of Limitations on IRS Collections
- IRS Collections Process Timeline
- IRS Revenue Officer Assigned to Your Case
- Innocent Spouse Relief Guide
- Tax Debt After Divorce
- Payroll Tax Problems for Businesses
- Trust Fund Recovery Penalty
- Can Chapter 7 Discharge Tax Debt?
- Florida Homestead and IRS Protection
- Tax Debt and Retirement Accounts
Math tells you what you owe. Strategy decides what you pay.
Tax attorney Darrin T. Mish represents individuals and businesses with IRS collection problems. Call the office to talk about your numbers.
Call (813) 229-7100