Getting a tax figure slightly wrong can cost a reader real money, so this page spells out who is responsible for what on IRSReliefGuide, how a calculator's math gets built, and how we handle a correction when someone flags one.
Ownership and accountability
Chris Terry owns IRSReliefGuide and signs off on every calculator's logic and this editorial policy. Guide and article writing is credited to the site's named contributor on the authors page; Chris does not byline articles here, his role is oversight, not reporting.
How a penalty or interest figure gets sourced
Nothing on this site starts from a blog post or a competitor's number. The failure-to-file and failure-to-pay penalties trace to Internal Revenue Code Section 6651. The installment-agreement thresholds and Offer in Compromise fee come from the applications and instructions IRS.gov publishes for those programs. The interest rate used in the calculators is pulled from the quarterly underpayment-rate revenue rulings the IRS issues, and updated when a new quarter's rate is announced.
How the calculator logic is reviewed
Each formula is tested against worked examples before it ships, and again whenever a rate or threshold changes. If the IRS adjusts a penalty percentage, raises a streamlined-agreement dollar limit, or resets the quarterly interest rate, the underlying constant in the calculator is updated and the change is reflected on the 2026 reference page, which lists the current figures with citations. Nothing typed into a calculator is transmitted to a server; the computation happens in the visitor's browser only.
What counts as a source here
The primary source for any figure is IRS.gov itself: the relevant IRS publication (Pub. 594 on the collection process, Pub. 505 on withholding and estimated tax), the applicable Internal Revenue Code section, or an official revenue ruling. Where a rule is genuinely unsettled, varies by circumstance, or depends on an IRS employee's discretion, such as whether a specific Offer in Compromise gets accepted, the guides say so plainly instead of implying a formula can predict the outcome.
Corrections
Spot a stale rate, a miscalculated example, or a citation that no longer matches the current rule? Send us the detail and the page. We check it against the source, fix confirmed errors promptly, and update the page's last-modified date when we do.
Independence from affiliate revenue
This site carries affiliate links, and clicking one that leads to a purchase may earn a commission. That relationship has no bearing on which calculators get built, what they return, or which programs a guide recommends. A firm does not get a better mention here for paying for one.