Guide
Invite codes compared with promo codes
How personal invites differ from public promotions at checkout.
In short: Referral codes tie a signup to another customer, while promo codes are usually broadcast discounts with different stacking rules.
Stacking rules
Providers often force a choice: either a referral invite or a public promo, not both.
Which should I use?
Compare the dollar value and eligibility rules; the better headline is not always the better outcome.