You may use Form 2848, Power of Attorney and Declaration of Representative for this purpose.

You should attach the document granting you power of attorney to the return. If your spouse cannot sign the return for any other reason, you may only sign it if you have a valid power of attorney.If you're the guardian for your spouse who is mentally incompetent, you may sign the return for your spouse as 'guardian.' Attach a statement that includes the form number of the return you're filing, the tax year, the reason your spouse cannot sign the return, and that your spouse has agreed to your signing for him or her. If your spouse cannot sign because of a medical condition and requests that you sign the return, sign your spouse's name in the proper place, followed by the word 'by' then your signature, followed by the word 'husband' or 'wife.' Be sure to also sign in the regular space provided for your signature. If you file a joint return, both spouses must sign the return.

For signing an electronic return see Validating Your Electronically Filed Tax Return.

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