Is there a certain format to use for a supplemental statement to attach to a form?

Unfortunately you cannot include a supplemental statement and E-file with TurboTax.

If you want (or need) to attach a statement, your return must be filed by mail.

 

Please see the IRS notes on HOW TO PREPARE YOUR TAX RETURN FOR MAILING 

Your Federal tax return goes to a different location depending on the state that you live in.  See this list to determine the location for you.

Where to File Paper Tax Returns (irs.gov)

 

Thanks for that information. However, my question was intended to be more general: does the IRS require a certain format for a supplemental statement that needs to be added to a form. I wasn’t inquiring about what is possible with TurboTax. 

There is not a set format, but certain things should be included:

 

An explanation letter to IRS should include the following writing items:

1. If you're responding to a notice, include the form and notice type.
2. Include Name, address, and contact information of the taxpayer.
3. The tax period.
4. The explanation of your issue or statement of information.
5. Facts or additional information supporting your position.