Why do I need to provide proof of my dependents?
The IRS expanded the tax-preparer due-diligence requirements to also include instances when they prepare returns for taxpayers filing as head of household (HOH). Filing under the Head of Household status and claiming credits for the dependents may provide significant tax benefits to the taxpayer.
Additional verification requirements
The tax preparer must complete the form https://www.irs.gov/pub/
"5. Did you satisfy the record retention requirement?
To meet the record retention requirement, you must keep a copy of your documentation referenced in 4b, a copy of this Form 8867, a copy of any applicable worksheet(s), a record of how, when, and from whom the information used to prepare Form 8867 and any applicable worksheet(s) was obtained, and a copy of any document(s) provided by the taxpayer that you relied on to determine eligibility for the credit(s) and/or HOH filing status or to compute the amount(s) of the credit(s)
List those documents, if any, that you relied on.
Leaving the list of documents blank may lead to a penalty of $540 imposed on the tax preparer.
Common documents to provide
Any document that shows your children's names and address matching your address is sufficient. Generally, school records are the easiest to obtain. Alternatively, medical bills or notes from a pediatrician's office should suffice.