Generally speaking, when it comes to a tax audit, the IRS and the various State Departments of Revenue can only go back three years from the date the original return was due, or from the date that you (the taxpayer) filed that tax return. In cases where law enforcement has reason to suspect (and this is a judgment call on the part of the auditor) that a taxpayer has understated their income by more than 25%, the statute of limitations is expanded to six years.
Once any given tax year, and a given taxpayer account, has been audited (examined) a first time, and closed . . . it is never audited again by the same revenue authority, unless some new evidence or previously unknown facts are later uncovered. However, that doesn't, say, prevent a state revenue authority from auditing a taxpayer's return for 2015 -- and then later, at some point in the future, the IRS also auditing (separately) that same 2015 tax year return. The reason for this is that the IRS and the state revenue authority are considered different taxing entities, and so they can initiate their own audits independently.
If you're just been notified by a state revenue authority of a multi-year audit, though, we would strongly and respectfully urge you to promptly seek professional audit representation. We have a specific recommendation for a company that is the preferred audit partner of Intuit; and it is the same one that you would be referred to if you have (or had) purchased the Audit Defense Guarantee package from within TurboTax.
Don't worry if you didn't purchase the audit defense at the time of your original tax preparation, because this company can still probably help you, and they can be hired "after-the-fact," so to speak, of receiving a taxpayer audit notice. Here is a link to TaxAudit.com:
https://www.taxaudit.com/
Another equally good option is to contact a local CPA or attorney in your local city or town. With multiple tax years potentially under audit by your state, you will want to respond to the state's auditor with good, professional-quality, representation. This is not a project you will want to handle completely on your own, without help, unless you are an accountant or an attorney yourself.
That is the best tax advice we can offer without knowing all of the relevant facts. We thank you for your question, and wish you good luck.
