If an invoice is changed in Xero, we will pick up the changes overnight and update our system. This means we cancel the currently pending payment, and re submit for the new amount/date etc.
Don't worry if you see a 'Cancelled Payment' notification from GoCardless, just check your Invoice Page in GoCardless for Xero and if the invoice is still showing as Pending Submission we have just cancelled, updated and re created the payment.
Also, if you update an invoice in Xero, but we don't cancel the payment, this is likely due to the fact the payment has already been submitted to the bank.
Please see : Updating Xero Invoices