“For a resubmission application, if I previously received NIAID’s agreement to accept assignment of a big grant for the new application, can I use the same acceptance letter?”

No, as indicated in our Big Grants SOP for investigator-initiated grant applications with total direct costs of $500,000 or more in any year of the grant, the big grant policy applies to an application whether it is new or a resubmission.

If you don't include a big grant acceptance letter as required, the NIH Center for Scientific Review will reject your application without a review.