Federal law requires you to maintain copies of your tax returns and supporting documents for three years. This is called the "three-year law" and leads many people to believe they're safe provided they retain their documents for this period of time.
However, if the IRS believes you have significantly underreported your income (by 25 percent or more), or believes there may be indication of fraud, it may go back six years in an audit. To be safe, use the following guidelines.
Create a Backup Set of Records and Store Them Electronically. Keeping a backup set of records -- including, for example, bank statements, tax returns, insurance policies, etc. -- is easier than ever now that many financial institutions provide statements and documents electronically, and much financial information is available on the Internet.
Even if the original records are provided only on paper, they can be scanned and converted to a digital format. Once the documents are in electronic form, taxpayers can download them to a backup storage device, such as an external hard drive, or burn them onto a CD or DVD (don't forget to label it).
You might also consider online backup, which is the only way to ensure that data is fully protected. With online backup, files are stored in another region of the country, so that if a hurricane or other natural disaster occurs, documents remain safe.
Caution: Identity theft is a serious threat in today's world, and it is important to take every precaution to avoid it. After it is no longer necessary to retain your tax records, financial statements, or any other documents with your personal information, you should dispose of these records by shredding them and not disposing of them by merely throwing them away in the trash.
While federal guidelines do not require you to keep tax records "forever," in many cases there will be other reasons you'll want to retain these documents indefinitely.