Brex pays out bonuses in the first few days of the month following the month the company you referred surpasses the $1,000 spend threshold. Brex sends an email to both parties (referrer / referred company) of the referral to celebrate.
You can also track your referrals in the Rewards > Referrals tab of the Brex dashboard. Each referral will show whether a company has been invited, whether they signed up, and whether the referral has been completed - please note the referral will not be complete until the referred company has spent $1,000 using Brex.