N.Y.C. Admin. Code § 24-606: § 24-606 Certificate of expenses.

Upon the completion of any response measure giving rise to a lien, the city agency implementing such response measure shall file with the agency or agencies designated by the mayor pursuant to section 24-605 a certificate setting forth the work done and the expenses incurred and certifying that such expenses were necessary and proper in the exercise of its lawful powers and, where applicable, apportioning such expenses among lots or buildings belonging to different persons. The city agency implementing such response measure shall also file a copy of any notices of potential liability for such expenses it has mailed for purposes of paragraph two of subdivision c of section 24-605 and a statement reciting the date of any such mailing.