I took cash the first time as they hadn't 'invited' us to invapay.
effectively , the pub sends you an email, you then have to follow a link to set yourself up .
You then take, or email the pub, an invoice for the gig fee and the pub then raise a payment ticket on invapay
The pub then pay invapay , who, a week later, pay you and charge 2.5% for the privilege , the money goes into the bank account you chose when you set up your invapay account.
I think you have to go to your account and confirm some details to approve the payment, but It is not an intuitive process on the whole.
I only do 3 gigs a year there so I have to think it through each time myself π€