If the referred customer spends:

£300 (net)           referrer gets a £25 Amazon voucher or 10% off their next order up to a value of £25

Over £400           referrer gets £35 Amazon voucher or 12% off their next order up to the maximum value of £35

£500 +                 referrer gets £50 Amazon voucher or 15% off their next order up to maximum value of £50