IRS Notice CP-48 is sent to inform a taxpayer that their Individual Taxpayer Identification Number (ITIN) must be renewed. ITINs now expire when they have not been used on at least one federal tax return for three consecutive tax years. Once an ITIN expires, it must be renewed before it can be used on a U.S. tax return. Taxpayers who do not need to file a federal return generally do not need to renew their ITIN. Certain dependents must provide additional documentation when applying for or renewing an ITIN. See the Instructions for Form W-7 for further requirements.