X is for X-Mark (Signature).
No matter how thorough and accurate your tax return is, it’s not considered a valid return unless you sign it. If you are filing a joint tax return, your spouse must also sign.
If you can’t sign your tax return for some reason, a representative can sign it on your behalf. You must have a Power of Attorney attached to the return that specifically authorizes the representative to sign your return. While a valid Power of Attorney under state law should suffice, the IRS really prefers to see an executed federal form 2848 (downloads as a pdf), assuming that there is no issue of capacity or other reason not to submit the form 2848.
If your child cannot sign his or her tax return, either parent can sign the child’s name. Underneath that signature, simply print “By (your signature), parent for minor child.”
Do not assume, however, that not being able to hold a pen properly or not being able to physically sign a return (because of, say, disability or illiteracy) means that you can’t sign your tax return. You may still be able to. An X mark is legal in most states as a valid signature. If all you can manage is an X, that’s your legal signature. Of course, it helps to have that signature witnessed (and some states may require that you do) in case there are any questions. But there’s nothing in the law that says that your signature must look a certain way, no matter what my fifth-grade teacher had me believe.
If you e-file your return, you must still “sign” the return. You do this by using a personal identification number (PIN). You can choose your own PIN using any combination of five numbers except for five zeros. And again, remember that a joint return requires two signatures: if you are filing a joint tax return, you and your spouse will each need to create a PIN and enter these PINs as your electronic signatures.
Finally, anyone you pay to prepare your tax return must sign it and include their Preparer Tax Identification Number (PTIN) in the space provided. The PTIN is mandatory for 2012; if your preparer doesn’t have one, you might want to find a new tax preparer.
