Final answer:
Customer checks received by an introducing firm should be made out to the clearing firm or brokerage holding and processing the customer's accounts and transactions, ensuring proper handling and regulatory compliance.
Step-by-step explanation:
When an introducing firm receives customer checks, the checks must typically be made out to the clearing firm or brokerage that holds customer accounts and processes securities transactions on behalf of the introducing firm. This ensures that the funds are directly deposited into the appropriate customer account and proper compliance with financial regulations is maintained. Depending on the relationship between the introducing firm and the clearing firm, policies may vary, but it's standard practice for checks to be written to the entity responsible for the financial management of the transactions.