Offering discounts or rewards to referees is a powerful strategy for improving signup conversion
cello_ucc
code.prefilled_promo_code
a promo code can be automatically passed to the UI. The form automatically picks up the parameter from the URL and pre-fills the promotion code field. More details can be found here.
Example:
10% off for 3 months via promo code CELLO
https://buy.stripe.com/cello?prefilled_promo_code=CELLO