When the bank is dealing with a new customer, it can hold some deposits before making the funds available for withdrawal. Regulation CC has special provisions for new account holders.
The account is not considered new if
each customer on the account had another established account at the bank within the preceding 30 calendar days; and
that established account was opened for at least 30 calendar days.
Different banks have different funds availability policy schedules when it comes to new accounts:
Cash, wire transfers, and Automated Clearing House (ACH) credit transfers are generally available the next business day after the banking day that they're deposited or received for deposit.
Official government checks (such as U.S. Treasury checks and state and local government checks), postal money orders, cashier's checks, certified checks, teller's checks, and traveler's checks deposited in amounts of up to $5,525 in one day are generally available in one or two business days after the banking day that they are deposited. However, the amount more than $5,525 might not be available until the ninth business day following the banking day on which the funds are deposited. Note that your bank may require the use of a special deposit slip for these kinds of checks.
Each bank may establish its own availability policy for all other checks deposited into new accounts.
Review your deposit account agreement for policies specific to your bank and your account.
Refer to 12 CFR 229 Availability of Funds and Collection of Checks (Regulation CC).