What is an audit? Types, process, and how to prepare

Published Monday 22 June 2026

Table of contents

• What is an audit?
• Types of audits
• What triggers an audit?
• The audit process
• How far back can the IRS audit?
• Why audits matter
• Your rights during an audit
• What happens after an audit?
• How to prepare for an audit
• Keep your financial records organized with Xero
• FAQs on audits

Key takeaways

• An audit is a formal review of your financial records to verify accuracy and compliance with tax laws or accounting standards.
• The IRS can generally audit returns from the past 3 years, but this extends to 6 years if income is understated by more than 25%.
• Keeping organized, up-to-date financial records is one of the most effective ways to prepare for an audit and reduce stress if one occurs.
• You have legal rights during an IRS audit, including the right to professional representation and the right to appeal any findings you disagree with.

What is an audit?

An audit is an independent examination of your financial records, statements, or tax returns to confirm they're accurate and complete. For small business owners in the US, audits most commonly involve the IRS reviewing a tax return, but they can also include internal reviews or third-party evaluations of your financial statements.

The goal of any audit is to verify that the numbers you've reported match your actual financial activity. Audits can be routine, random, or triggered by specific red flags in your records. While the word "audit" can feel intimidating, understanding what's involved helps you stay prepared and confident.

Types of audits

Not all audits work the same way. The type of audit you encounter depends on who's conducting it and why.

• Tax audit: Conducted by the IRS or a state tax authority to verify the accuracy of your tax return. Tax audits can be handled by mail (correspondence audit) or in person at an IRS office or your place of business. Accurate tax return preparation is one of the best ways to avoid triggering a tax audit.
• External audit: Performed by an independent certified public accountant (CPA) or accounting firm. External audits provide an objective opinion on whether your financial statements are fairly presented. Lenders, investors, and regulatory bodies often require them.
• Internal audit: Carried out by someone within your organization, or a hired consultant, to evaluate your internal controls, processes, and risk management. Internal audits help you catch errors and inefficiencies before they become bigger problems.
• Compliance audit: Focuses on whether your business is following specific laws, regulations, or industry standards. For example, a compliance audit might check that you're meeting payroll tax requirements or adhering to data protection rules.

What triggers an audit?

Understanding what prompts the IRS to look more closely at a return can help you avoid common mistakes.

The IRS uses several methods to select returns for audit:

• Computer screening: The IRS runs every return through its Discriminant Information Function (DIF) system, which scores returns based on the likelihood of errors. Higher scores increase your chances of being selected.
• Document mismatches: If the income reported on your return doesn't match the W-2s, 1099s, or other information documents the IRS receives from third parties, your return may be flagged.
• Random selection: Some returns are chosen purely at random as part of the IRS's National Research Program.
• Related examinations: If a business partner, investor, or related party is being audited, the IRS may also review your return.
• Unusual deductions: Claiming deductions that are disproportionately large compared to your reported income, such as excessive home office or vehicle expenses, can draw attention.
• Unreported income: Failing to report all sources of income is one of the most common audit triggers.

The audit process

If you're selected for an IRS audit, the process typically follows a structured series of steps. Knowing what to expect makes it easier to respond.

1. Notification

The IRS notifies you by mail with a letter that explains which return is being reviewed and what information you'll need to provide. The IRS doesn't initiate audits by phone or email.

2. Document gathering

You'll need to collect the records specified in the notification letter. This usually includes receipts, bank statements, invoices, and any documentation that supports the items on your return.

3. Review

For a correspondence audit, you mail the requested documents to the IRS. For a field audit, an IRS agent visits your place of business or your accountant's office. An office audit requires you to visit an IRS office with your records. Field and office audits involve a face-to-face interview and a more detailed review.

4. Findings

Once the review is complete, the IRS sends you a letter with their findings. You'll have the option to agree, partially agree, or disagree with the results.

How far back can the IRS audit?

The IRS has time limits on how far back it can go when reviewing your returns, but those limits vary depending on the circumstances.

• 3 years: The standard statute of limitations. The IRS generally has 3 years from the date you filed your return to initiate an audit.
• 6 years: If the IRS finds that you underreported your gross income by more than 25%, the window extends to 6 years.
• No time limit: There's no statute of limitations if you filed a fraudulent return or didn't file a return at all.

Because of these rules, tax professionals commonly recommend keeping tax records for at least 7 years. For small business owners, storing your records digitally in cloud accounting software makes it simpler to access past documents quickly if needed.

Why audits matter

Audits serve a purpose beyond checking boxes for compliance. They can be genuinely useful for your business.

• Compliance: Audits confirm that your business is meeting its tax obligations and following applicable regulations. Staying compliant helps you avoid penalties, interest charges, and legal issues.
• Credibility: A clean audit history builds trust with lenders, investors, and potential partners. If you're applying for a business loan or seeking outside funding, audited financial statements carry more weight.
• Better decision-making: The process of preparing for an audit often reveals gaps in your record keeping or small business accounting processes. Addressing these gaps gives you clearer, more reliable data to base decisions on.
• Error detection: Audits can uncover bookkeeping mistakes, duplicate entries, or missed deductions that you might not have caught on your own.

Your rights during an audit

If you're audited by the IRS, you're protected by the Taxpayer Bill of Rights. Knowing your rights can help you stay in control throughout the process.

• Right to representation: You can have a tax professional, such as a CPA, enrolled agent, or attorney, represent you during an audit. You don't have to face the IRS alone.
• Right to professional and courteous treatment: IRS employees are required to treat you with respect. If you feel you've been treated unfairly, you can report it to the IRS.
• Right to appeal: If you disagree with the audit findings, you have the right to appeal within the IRS before going to court. The IRS Independent Office of Appeals handles these cases.
• Right to confidentiality: The IRS can't share your tax information with outside parties without your authorization, except as required by law.
• Right to finality: You have the right to know the maximum amount of time you have to challenge the IRS's position and the maximum amount of time the IRS has to audit a particular tax year.

What happens after an audit?

Once the IRS finishes reviewing your records, there are 3 possible outcomes.

• No change: The IRS finds that everything on your return is accurate. No additional taxes, penalties, or adjustments are needed.
• Agreed: The IRS proposes changes, and you agree with them. You'll sign the examination report and pay any additional tax owed, plus interest.
• Disagreed: You don't agree with the IRS's findings. In this case, you can request a meeting with an IRS manager, file an appeal with the IRS Independent Office of Appeals, or take the matter to tax court.

If you owe additional taxes after an audit, the IRS offers payment plan options so you can settle the balance over time rather than in a single lump sum.

How to prepare for an audit

The best time to prepare for an audit is before you're ever notified of one. Good financial habits year-round make the process far less stressful.

1. Keep thorough records

Save receipts, invoices, bank statements, and any documents that support items on your tax return. Digital copies are acceptable and easier to organize.

2. Reconcile accounts regularly

Match your bank and credit card transactions to your books at least monthly. Regular bank reconciliation catches errors early and keeps your records accurate.

3. Separate business and personal finances

Use a dedicated business bank account and credit card. Mixing personal and business expenses creates confusion and makes it harder to substantiate deductions.

4. Document deductions carefully

For each deduction you claim, keep proof of the amount, the business purpose, and the date. This is especially important for travel, meals, and vehicle expenses.

5. Review your return before filing

Double-check that all income sources are reported and that the figures on your return match your supporting documents.

6. Hire a tax professional

A CPA or enrolled agent can help you file accurately and represent you if an audit occurs. You can find an accountant or bookkeeper through the Xero advisor directory. Their expertise is especially valuable for complex returns.

7. Store records for at least 7 years

Keep your tax records and supporting documents for a minimum of 7 years to cover the IRS's extended audit window. A tax preparation checklist can help you stay organized.

Keep your financial records organized with Xero

Staying audit-ready starts with keeping your financial records accurate and easy to access. Xero's cloud accounting software connects to your bank to pull in transactions automatically, helping keep your books up to date.

With features like automated bank reconciliation, digital receipt capture through Hubdoc, and customizable financial reports, Xero gives you the tools to help stay on top of your finances and reduce manual effort. If an audit ever comes your way, you'll have the records you need in one place, ready to go. Get one month free.

FAQs on audits

Here are answers to some frequently asked questions about audits.

How long does an IRS audit take?

A simple correspondence audit can wrap up in a few months, while more complex field audits may take over a year. The timeline depends on the issues being reviewed, how quickly you provide documentation, and IRS staffing.

Can you get audited if you don't file taxes?

Yes. If you don't file a return, the IRS can file a substitute return on your behalf and assess taxes owed. There's also no statute of limitations for unfiled returns, so the IRS can come back to you at any time.

How much does an audit cost a small business?

The cost depends on the type of audit. An IRS tax audit has no direct fee, but you may incur costs for professional representation, which can range from a few hundred to several thousand dollars. A voluntary external financial audit by a CPA firm typically costs between $5,000 and $15,000 for a small business.

Do small businesses get audited more than individuals?

Not necessarily. The IRS audits a relatively small percentage of all returns each year. However, sole proprietors and businesses with significant cash transactions or large deductions relative to income may face higher scrutiny.

What documents do you need for an audit?

You'll typically need bank statements, receipts, invoices, payroll records, prior tax returns, and any documents that support the income and deductions on the return being audited. The IRS notification letter specifies exactly which records to provide.