The effective date is usually supposed to be the date the VA received the claim that led to the award. If you ever let a claim lapse and didn't appeal it, you cannot use that as the effective date. I have never heard of an effective date having anything to do with an "NOD reply" or any denial date. If there is a big discrepancy between the effective date they assigned and the date of the live pending claim, you should appeal the decision and ask them to verify the effective date. Good luck, and feel free to email me directly with any questions at fight4veteransrights@yahoo.com