Lauren Babus said: I could understand if it wouldn't let me enter the CUSIP for any type of bond but this really defies logic!
You are not being prevented from entering the CUSIP; you are being prevented from entering the Ticker "Symbol".
A CUSIP is NOT a ticker symbol. The value you enter in the "Symbol" field of a bond is not a CUSIP to Quicken ... it's just a ticker symbol ... and not a valid ticker symbol at that, since bonds do not have ticker symbols.
[Still, in my opinion, you should not be prevented from putting a value in the ticker Symbol for any Quicken security (see below).]
As I noted earlier, a user can never enter a true CUSIP in Quicken; only Quicken can do that. While Quicken can store CUSIP numbers, the Quicken CUSIP field is read-only.
If you download investment account data, and any of the securities you download have CUSIP numbers, you can see their CUSIP ID's (as suggested earlier in this discussion) by Editing the security in the Security List and clicking the "Other Info" button in the Edit Security Details dialog. There - if the security has a CUSIP and you have downloaded that security from your financial institution - you will see the value of the "CUSIP ID" for your security ... not the value of the ticker "Symbol".
[As I recall, there is one reason to want to enter a value in the Quicken security "Symbol" field, even for securities that have no ticker symbol: it has to do with the ability to recover security prices and needing a ticker symbol to insure that the prices for a given security can be identified. But you certainly did not say that was your interest; and even if it was, you would not need a CUSIP ID to accomplish that - any unique value in ticker symbol would do the trick.]