We are defined by our words, so use them with care.
Failure to make the verb agree in number with the subject is a common mistake, even among experienced and talented writers. Improper conjugation usually occurs when collective nouns are used.
Note that the subject of the sentence is a group, not banks, so the verb to be takes a singular form. Avoid the British usage found most commonly in sports stories: Manchester United are playing Tottenham this evening. Correct: Manchester United is playing Tottenham this evening.
The following words are usually regarded as singular nouns: committee, staff, ...