If your home or business address has changed, make sure that you update this information with the IRS to ensure that you receive any refunds or correspondence from them. Since the IRS meets its notice requirements by sending notices to your last known address, it is not an excuse that you did not receive the correspondence if you have not provided the new information.
Although no one likes to receive mail from the IRS, other than a refund check, it is important that you timely receive their correspondence and respond promptly. Otherwise, the IRS will automatically escalate the inquiry, making it far more difficult to deal with. If additional tax will be owed as a result of an inquiry, penalties and interest will continue to accrue.