What is the penalty for a tax return filed with an accuracy error based on substantial understatement or negligence?

The correct answer reflects the fact that the penalty for a tax return that contains an accuracy error resulting from substantial understatement or negligence is set at a flat rate of 20% of the net understatement of the tax. This penalty is assessed when the taxpayer does not exercise due diligence in understanding the tax laws or fails to report accurate information, which leads to owing more tax than necessary.

In tax regulations, substantial understatement is defined as reporting an underpayment that is significantly lower than what is actually owed. This can occur due to incorrect calculations or misinterpretations of tax law. As a deterrent against such negligence or substantial errors, a penalty is imposed to encourage taxpayers to file accurate returns and uphold their responsibility in reporting their income and taxes correctly.

Understanding this penalty provides insight into the broader framework of tax compliance, emphasizing the importance of careful and accurate reporting to avoid additional costs and potential legal implications.