1- Incorrect or missing social security number
This is a common mistake constantly noted by the IRS. The Social Security number for the taxpayer, spouse, dependents, and children who qualify for the Earned Income Credit or Child Tax Credit, must be written on the return form exactly as they appear on the Social Security Card. Always double-check.
2- Misspelled or different names
Although the IRS is all about numbers, words are important too. When your name or the name of your spouse, children, etc. do not match, this causes the to IRS to slow down the processing time on your tax return or throw it out completely. One common cause is when a taxpayer legally changes their name, most notably after getting married.
“Remember to notify the Social Security Administration of your name change after your wedding”
3- Failing to sign/ date a return
Sounds simple, yet every year, hundreds commit this common mistake of forgetting to sign their tax return. The IRS won’t process your return it if it’s missing a signature, even on e-filed returns. The IRS does not accept tax returns that are not signed, Period.
“Both spouses must sign a joint return.”
For more information please visit: http://www.irs.gov/taxtopics/tc303.html