I have a component
select and it has a lot of information about Bank accounts. I need to improve it because this component will have more then 300 bank accounts. Is it a good idea to put in order the bank accounts?
If the user is almost always entering account numbers from the bank they work at, you could use a prefix, and save them from typing.
I don't know details of your use case, but you can arrange the search input so users can save some typing by prefixing any non unique digits, especially if this is a common and repetitive task:
You need to determine how the people selecting the account is making that selection. Is it by the last digits? By the first digits? Are the accounts associated with a person or company?
In any of these cases, you can add an active search by the last digits and you can also bold them if they are associated with a company or person you could also display the owner name on the right of each account.
Simply categorizing them to represent visually hierarchical demonstration to let user possibly differentiate the list items while eliminating them starting from the ancestors through all over the list might get help.
P.S.: Since you didn't specified any proper information about pre-fixed numbers possibly included within these accounts, I presented the second example below which is probably more suitable according to your specific case.
You may take a look at it on Codepen.io also.