All of these are due diligence requirements for a paid preparer who files a federal return for a taxpayer claiming one or more refundable credits EXCEPT:

Complete and file Form 8867, Paid Preparer's Due Diligence Checklist.

Complete copies of all worksheets used to calculate any federally refundable credit.

Notarize all supporting documentation.

Ask the taxpayer additional questions as needed to obtain relevant information. Document both the questions asked and the taxpayer's response to each question