How does IBKR determine the amount of shares which are eligible to be loaned?

A Payment in Lieu, (PIL) refers to a cash credit or debit made to an account in recognition of a cash dividend paid to stockholders of the issuer.

Received…

The first step is to determine whether securities are considered fully-paid for or if they are rehypothecated as collateral for a margin loan balance.  A broker who finances client purchases of securities via margin loan is allowed by regulation to loan or pledge as collateral that client’s securities in an amount of 140% of the cash debit balance. For example, if a client maintaining a cash balance of $50,000 buys securities with a market value of $100,000, the debit balance will be $50,000.  The broker holds a lien on 140% of that balance or $70,000 of securities. Any securities held by the client in excess of that amount are referred to as excess margin securities ($30,000 in this example) and are required to be segregated unless the client provides authorization to Interactive Brokers LLC to lend through the Stock Yield Enhancement Program.  Note that only $30,000 of securities is eligible to be lent via SYEP…

No. The Stock Yield Enhancement Program is entirely managed by IBKR who, after determining those securities, if any, which IBKR is authorized to lend by virtue of a margin loan lien, has the discretion to determine whether any of the fully-paid or excess margin securities can be loaned out and to initiate the loans…

Fully-paid securities are securities in a customer's account that have been completely paid for. Excess margin securities are securities that have not been completely paid for, but that represent the aggregate loan value and market value of each class or series of security required to be segregated for each client as determined under CIRO Rule 4316 divided by the loan or market value, as the case may be, of one unit of the security…