Offer a fixed (e.g., $25 off) or percentage discount (e.g., 10% off) to someone who is recommending your product or service. However, according to tests conducted by Annex Cloud, fixed dollar amounts are more compelling than a percentage off the purchase.
The timing for asking for referrals is also crucial: Don’t expect someone to provide a recommendation if he’s not completely satisfied. Ask them when they’re already on a dopamine high; right after a successful purchase, or after completing an important or lengthy task in your application.
Source - DigitalPsychology.io