Hi, I'm trying to raise a new invoice but the invoice number coming up automatically is one I've already used. Can anyone let me know how I fix this please?

Hello Caroline-lofts-p, 

Welcome to the Community page, 

When you're creating a new invoice, if you click on the invoice no. box and change it to what the next number should be so for example if it is saying you have 1018 twice if you change the number to 1019 then when you save your invoice and go to do another one it will then go onto invoice 1020 automatically for you so you can then carry on.