There is an IRS tax penalty for situations where you do not supply your social security number on tax returns. This applies to both you and any dependents you are claiming on your income tax return. You must include all applicable social security numbers. If you do not, the IRS penalty will be $50 for each failure.
Another situation in which you will be penalized by the IRS involves failing to give your social security number to a third party (such as a bank, or other financial institution) when it is required on a statement, return, or other documents. This is another situation where you will be assessed a $50 penalty by the IRS.
This is a perfect example of why it is important to double-check your income tax return prior to submitting to the IRS. Make certain you include all of your required social security numbers on your income tax return.
If you can show the IRS that the reason you failed to supply a social security number was due to a reasonable cause and not willful neglect, you will not be penalized.