What is the date to be placed on the Adverse Action Notice? Is it the date the notice is filled out or the date the credit is denied?

The regs do not require what the date should be. To me you put the date the notice was created to prove to the regulators that the notification was sent within the appropriate time requirements. See below the content requirements for consumer adverse actions.

From 202.9(a)(2)
Content of notification when adverse action is taken. A notification given to an applicant when adverse action is taken shall be in writing and shall contain a statement of the action taken; the name and address of the creditor; a statement of the provisions of § 701(a) of the Act; the name and address of the federal agency that administers compliance with respect to the creditor; and either:
(i) A statement of specific reasons for the action taken; or
(ii) A disclosure of the applicant’s right to a statement of specific reasons within 30 days, if the statement is requested within 60 days of the creditor’s notification. The disclosure shall include the name, address, and telephone number of the person or office from which the statement of reasons can be obtained. If the creditor chooses to provide the reasons orally, the creditor shall also disclose the applicant’s right to have them confirmed in writing within 30 days of receiving the applicant’s written request for confirmation.

That is my mindset as well; however, a recent exam hit us on using the Adverse Action preparation date rather than the date of denial.

We were criticized once because an Adverse Action for a HMDA reportable-denial, didn't have the same date as the decision made by the "Second Review Committee".

My two cents worth. We have, and previous employers also, have always used the date the notice is prepared. With the exception of a couple of scenarios Reg B requires you to give written notice of the adverse action. The exceptions are certain business credit requests and a small institution that takes less than 150 (I think without looking it up) credit request in the preceding year. We have never been criticized for using this date. I have seen scenarios where a verbal declination was given and before the AAN was sent the applicant called back with additional information and the decision was reversed. We take the stance the "final" decision occurs when the written notification is given.

OSC 202.9

3. When notification occurs. Notification occurs when a creditor delivers or mails a notice to the applicant's last known address or, in the case of an oral notification, when the creditor communicates the credit decision to the applicant.