An understatement is considered to be substantial if it is more than the greater of:
- 10% of the tax required to be shown on the return, or
An “understatement” is the amount of tax required to be shown on your return for a tax year minus the amount of tax shown on the return, reduced by any rebates. The term “rebate” generally means a decrease in the tax shown on your original return as the result of your filing an amended return or claim for refund. For items other than tax shelters, you can file Form 8275 or Form 8275-R to disclose items that could cause a substantial understatement of income tax. In that way, you can avoid the substantial understatement penalty if you have a reasonable basis for your position on the tax issue.
Disclosure of the tax shelter item on a tax return does not reduce the amount of the understatement. Also, the understatement penalty will not be imposed if you can show there was reasonable cause for the underpayment caused by the understatement and that you acted in good faith. An important factor in establishing reasonable cause and good faith will be the extent of your effort to determine your proper tax liability under the law.