TurboTax provides for entering an explanation where it is required by IRS rules. The IRS does not want explanations that are not required by the rules. The IRS instructions for Form 1040 say "Don't attach correspondence or other items unless required to do so." If the IRS has a question about your tax return or wants more information, they will send you a letter asking for it.
You should include the fraudulent 1099-NEC in your tax return, and enter a business expense of an equal amount to offset the 1099-NEC income. You could enter the business expense with a short description such as "Incorrect 1099-NEC" or "Fraudulent 1099-NEC." Then you can e-file the tax return. If the IRS wants more detail they will contact you.
