When we talk about an amount of money as a whole, a singular verb is used.
- £1500 is not a small amount.
(we are talking about one £1500 amount so a singular verb/is)
When we talk about money, but we are thinking about the notes or coins as separate things, a plural verb is used.
- Five £10 notes were given to the winners.
(we are talking about five winners and five £10 notes so a plural verb/were)
