What Actually Triggers an Audit

Almost everything people call getting audited is a letter generated by a computer that already had a copy of a document you left off your return. The fear and the mechanism have very little to do with each other, and the fix for one is not the fix for the other.

Two different machines are at work. One compares the documents third parties filed about you against the numbers on your return. The other scores returns for examination. Most of the mail people panic about comes from the first one.

A CP2000 is not an audit

A CP2000 says one thing: a third party reported this figure, your return shows another, here is the tax we think the difference creates, respond by the date printed on the notice. No examiner is assigned. Nobody is asking about your mileage log. If the notice is right, you agree and pay. If it is wrong, and plenty of them are, you write back with the explanation and the documents behind it.

The most common wrong one I see is a 1099-K reporting gross payment volume while the Schedule C reports deposits net of processor fees. Same income either way, same profit at the bottom. But gross is the figure the matching program compared against, so the return has to show gross receipts up top with the fees taken as an expense below. Identical tax, no letter.

Real examinations exist, and most of them also arrive as mail. The IRS names two or three line items and asks you to prove them. An agent sitting at your conference table reviewing everything is the unusual case, not the default one.

The scoring system compares your return against statistical norms for returns of similar size and type. The IRS calls it the Discriminant Function score and has never published the formula. What that means practically is that nothing on your return is judged in isolation. Vehicle expense that is unremarkable next to a contractor's gross receipts is conspicuous next to a small consulting income, and the number itself never changed.

Round numbers draw attention for a related reason. Real expenses have cents in them. A column of figures all ending in three zeros tells the reader somebody estimated, and an estimate is a position you may not be able to support two years later.

What does not deserve the fear it gets

The home office deduction. The standard is exclusive and regular business use of the space. Exclusive is the word doing the work. The end of the dining table where you also eat dinner fails. A spare bedroom that is only ever your office qualifies. If you clear that bar, take the deduction. The simplified method is $5 per square foot up to 300 square feet, capped at $1,500, with no depreciation schedule to maintain.

One caveat catches employed people constantly. If you are a W-2 employee, you generally cannot claim a home office at all, because the TCJA suspended unreimbursed employee business expenses. Your fix is an accountable plan reimbursement from your employer, not a line on your return.

An extension. Form 4868 moves the filing deadline for a 2026 individual return from April 15, 2027 to October 15, 2027. It is granted automatically and requires no reason. It changes the date on the return, not what is on it, and the scoring works on what is on it.

An amended return. A Form 1040-X cannot be handled by matching, so a person reads it. That review is about the change you made. If you find a real error, correcting it beats hoping. The alternative is leaving a known mismatch on file with a copy of the contradicting document already sitting on the other side of it.

The real risk is not selection. It is substantiation.

This is the part I would rather you take away than the trigger list. Your odds of being examined are low. Your odds of coming out of an examination intact depend entirely on records you either kept at the time or did not.

Deductions are a matter of legislative grace, which is the courts' way of saying the burden sits with you. Nobody has to disprove your mileage. You have to prove it. Reconstructing a year of business driving from credit card statements eleven months later is exactly where people lose deductions they were fully entitled to claim.

So I care considerably more about how a client keeps records than about how aggressive a position is. Well documented positions usually survive scrutiny. Modest positions with nothing behind them frequently do not.

What audit-resilient actually looks like

It is a boring list of habits. A mileage log written the week the driving happened, not the week the notice arrives. Receipts filed by tax year in one place you can find under pressure. A business bank account that is not also where the groceries come out.

Travel, meals, gifts and vehicles are the categories with their own statute, Section 274(d), and it wants amount, date, place and business purpose. Three of those four are printed on the receipt. The fourth is the one you have to write down at the time, because in March you will not remember who you ate with in June.

Then, before the return goes out, reconcile your gross receipts against the gross figure on every 1099-NEC and 1099-K you received rather than against your deposits. That single check heads off most of the mail.

Retention periods track the statute of limitations, which answers the question people are really asking: how long can this come back.

Those come from IRS Topic 305, and the record retention page breaks them out by document type.

If a notice is already in your hands, the response window printed on it is real and short. That work is IRS problem resolution, and as a CPA I can represent you directly under a Form 2848 power of attorney. If you are still weighing whether a position on this year's return is worth taking, that conversation belongs in return preparation, before the return is signed rather than after.

And if your return is one W-2 and the standard deduction, none of this is your problem. There is nothing on that return to select. Send me the details if you are not sure which of those describes you.