When you move to a new residence, it is necessary for you to notify the Internal Revenue Service of your change of address using Form 8822. If you neglect to do so, IRS may send important correspondence (e.g. refunds and notices) to your old address. If for some reason the Post Office fails to forward the IRS correspondence to you, or only forwards it after a lengthy delay, the consequences could be costly.

To meet its responsibilities in many cases, IRS doesn’t have to prove delivery. All it has to do is send correspondence to your “last known address.” The “I never got it” defense is lost if IRS properly sent the notice to your old address.

For example, if you move after filing a return and IRS mails a refund check to your old address, the refund may be delayed and IRS won’t owe you any interest for the delay.

Similarly, if IRS sends a notice of a tax deficiency to your old address, you may never receive it. After 90 days, you will lose the right to contest the matter in the Tax Court. While you can still wage the battle in federal district court, you will have to pay the tax first, and there may be other tactical disadvantages of doing so.

In addition, if you do owe tax and are delayed in learning about it, the penalties and interest costs will accrue even though you didn’t know you had an outstanding tax liability.

There are other notices IRS must send to you before taking certain actions affecting you (such as contacting third parties about your tax situation, issuing summonses, putting liens on your property, etc.). These other notice situations don’t arise often, but if they do they are serious. You can best protect your rights if you know as early as possible what IRS is doing. So it’s in your interest to keep IRS informed about your current address.

Once you file a tax return showing your new address, IRS will make the change itself but only after the return is processed, which could take many weeks after you file. IRS is also required to update your address in its files to reflect any permanent forwarding address you give to the U.S. Postal Service, but that updating also could take time. To be safe, you should notify IRS of the change directly.