Given its tax time, you will likely find long lines at your local post office. Individuals are filing tax returns, so those who don’t efile must mail the returns. When you mail anything, you should seal the envelope; that’s especially true for anything with your social security number on it.
Yet here’s an unfortunately true story told to me by a fellow tax professional. One of her clients mailed his tax return to the IRS but forgot to seal the envelope. The return did make it to the IRS, but without page two of Schedule C. The first that the client found out there was a problem was when the IRS sent him a letter noting the omission. The second time he knew that there was a problem was when she found she was a victim of identity theft.
The client blames himself for his stupdity. This particular identity thief was caught, and the damage done to the individual who forgot to seal the envelope was minimal.
So when you file your tax return, do seal the envelope. Or better yet, use electronic filing and you can avoid the post office and this issue completely.