There are a number of different ways.

You could present them with or email them a voucher and they would then call the freephone number on the voucher to request payment. They could also logon to their online account and request payment from there.

There is a system called 'Autopay' that parents and carers can use. If both parties choose to use the 'Autopay' system the funds are automatically transfered on the voucher 'valid from' date as long as cleared payment has been received from the employer.

You could also issue a voucher from your prepay account and payment is sent to the carer the following day.