Thank you for your question. Some notes, such as scrip notes, may not have catalog numbers. In a case of scrip notes, we do not charge if you do not list those. For regular notes or confederate notes, you can put the regular Friedberg number. If you are not certain, put the number you think it is and we will double check it when it comes in. As long as you make an attempt to list the catalog number, you will not be charged. You can find these FR numbers in the book, "Paper Money of the United States" by Arthur and Ira Friedberg.
If you have any other questions, please let me know. Thank you.