As per SEC Rule 172-5(f)(2): Every broker or dealer that is required to file an annual report of financial statements section shall file no later than December 10 of each year a statement with the Commission’s principal office in Washington, DC, the regional office of the Commission for the region in which its principal place of business is located, and the principal office of the designated examining authority for such broker or dealer. Such statement shall indicate the existence of an agreement dated no later than December first, with an independent public accountant covering a contractual commitment to conduct the broker’s or dealer’s annual audit during the following calendar year. (ii) The agreement may be of a continuing nature, providing for successive yearly audits, in which case no further filing is required. If the agreement is for a single audit, or if the continuing agreement previously filed has been terminated or amended, a new statement must be filed by the required date.In summary, you must have an executed engagement letter for your annual independent audits (which must be conducted by a PCAOB approved CPA firm) by December 1st, and if your engagement letter does not have language stating that it is of a continuing nature, providing for successive yearly audits.