Hi, I'm Patrick, and I work for the IRS. If you received a letter CP3219A, Statutory Notice of Deficiency, and are wondering what to do, this may help. The letter explains why there is a proposed increase in your tax and what to do if you don't agree. Before receiving it, you would have received an earlier letter, usually a CP2000, explaining that our records don't match the information you reported on your tax return. If we didn't hear from you or couldn't resolve the issue with the information you gave us, we send you another letter. This letter explains the changes and your right to challenge the increase in Tax Court. Review the changes and compare them to your tax return. If you agree, sign the enclosed Form 5564 and mail or fax it to the address or fax number listed on the letter. If you are making a payment, include it with the Form 5564. If you pay the amount due now, you will reduce the amount of interest and penalties. If you don't agree, respond to the IRS immediately. Send us a signed statement with any documents or explanation you want us to consider. Send photocopies, not original documents. Sending us additional information won't extend the deadline to file a petition with the Tax Court. Mail or fax your response to the address or fax number listed on the letter. Include your name, Social Security number and tax year on each page. If your explanation is accepted, we will send a letter confirming the issue is resolved. If you are going to challenge it, you must file a petition with the U.S. Tax Court, not the IRS, and we will no longer be able to work directly with you. File your petition within 90 days from the date on the letter, or 150 days if it's addressed to a person outside of the United States. The Tax Court cannot consider your case if the petition is filed late. If we don't hear from you or you don't petition the court, we will send you a bill for the additional tax and applicable penalties and interest. To learn more, go to IRS.gov and search for CP3219A or Publication 5181.