N.Y.C. Admin. Code § 3-220: § 3-220 Retention of records.

Every person to whom this subchapter is applicable shall keep for at least five years a detailed and exact account of:

(a) all compensation of any amount or value whatsoever;

(b) the name and address of every person paying or promising to pay compensation of fifty dollars or more and the date thereof;

(c) all expenditures made by or on behalf of the client; and

(d) the name and address of every person to whom any item of expenditure exceeding fifty dollars is made, the date thereof and receipted bill for such expenditure.