Which of the following is a due diligence requirement for a paid preparer who files a federal return for a taxpayer claiming one or more refundable credits?
1) Ask the taxpayer additional questions as needed to obtain relevant information
2) Document the questions asked and the taxpayer's response to each question
3) Audit all supporting documentation
4) Complete all worksheets used to calculate any federally refundable credit
5) Inform the taxpayer that they must file Form 8867, Paid Preparer's Due Diligence Checklist, after their return is submitted to the IRS
6) Maintain a copy of the completed Form 8867, Paid Preparer's Due Diligence Checklist, and any other documents relied on to complete the form or any of the accompanying worksheets, for at least five years after the due date of the return