Question: I have a client that recently received a valid Social Security Number. He was previously filing with an ITIN. The client is considered a U.S. resident for tax purposes (even in prior years) based on substantial presence. In 2018 he received his social security number, but he has 2 different w-2 forms with 2 different socials for different. One is his "real" SSN that he was given, and the other is a "made-up" social he used for almost all year up until November. I know that will cause an issue with the IRS if I just file it with his real social so anyone can tell me how to approach this?

Christy's Answer: If a taxpayer has a valid Social Security Number, that is the number that should be used on all the taxpayer's returns (this applies even if you are preparing prior years). So, use the SSN on all returns. Some software will still allow you to e-file, even if you have a SSN mismatch.

I have heard of tax professionals having problems with this in the past, usually with the taxpayer not getting proper credit for tax withholding. So I personally do not advise e-filing when you have an SSN/ITIN mismatch. The easiest solution is to file on paper and include a copy of all the taxpayer's W-2 forms, showing the withholding amounts. I’ve done this process dozens of times with no issues. You don’t need to include any type of explanation (the IRS knows what's going on, this is a common enough issue). You will have to do the same for the state, too. The paper filed returns will generally have a longer processing time, but beyond that, there are typically no issues.