If a customer comes in and opens up several new accounts with separate with separate checks, what availability standards apply. So, customer opens 4 accounts with a $10,000 check for in each account. Only $5,525 total available or that amount times 4?

For other situations where a release of funds is done, such as with the first $225 in general and with the first $5,525 for the large hold, then it is clear that you aggregate deposits even across multiple accounts. So, Reg. CC as a general methodology seems customer based.

[b. Special rules also apply to deposits of Treasury checks, U.S. Postal Service money orders, checks drawn on Federal Reserve Banks and Federal Home Loan Banks, state and local government checks, cashier's checks, certified checks, teller's checks, and, for the purposes of the new account exception only, traveler's checks. The first $5,000 of funds deposited to a new account on any one banking day by these check deposits must be made available for withdrawal in accordance with § 229.10(c). Thus, the first $5,000 of the proceeds of these check deposits must be made available on the first business day following deposit, if the deposit is made in person to an employee of the depositary bank and the other conditions of next-day availability are met. Funds must be made available on the second business day after deposit for deposits that are not made over the counter, in accordance with § 229.10(c)(2). (Proceeds of Treasury check deposits must be made available on the first business day after deposit, even if the check is not deposited in person to an employee of the depositary bank.) Funds in excess of the first $5,000 deposited by these types of checks on a banking day must be available for withdrawal not later than the ninth business day following the banking day of deposit. The requirements of § 229.10(c)(1)(vi) and (vii) that “on us” checks and the first $100 of a day's deposit be made available for withdrawal on the next business day do not apply during the new account period.]

However, with a literal reading of this section that says, "the first $5,000 of funds deposited to a new account," and nothing else to say otherwise, it would seem to be account based for this type of situation.