Available Balance of Savings Accounts, Explained:

The available balance is the current balance that is accessible to the customer who's name is listed on the account. Notable is that deposits that have not posted to the account are often posted partially, until the funds in the process of collection, have cleared. Also, a cash reserve might be accounted for in the available balance, although its true intent is to act as a modest line of credit that prevents overdraft fees for the check maker. See overdraft protection.

When deposits to accounts are made, it is often helpful to know the individual bank or savings institutions policy for posting deposits as available funds. As an example, many banks post deposits made before Friday afternoon, the following monday, skipping, to three days later. With this in mind, depending on the time horizon needed for completing the funds in collection, it could be more wise to deposit on weekdays prior to Friday and even Thursday if at all possible, to expedite funds transfer. To do so could imply requesting that checks and payments for deposit be received earlier in the week.