Your fintech runs three KYC tiers. Tier 1 (basic phone-number verification) caps wallet balance at ₦300,000. Tier 2 (full ID) caps at ₦5,000,000. Tier 3 (biometric + address) is unlimited. When a deposit would push a user's wallet over their tier cap, you don't just block it, you accept the cash AND park the overflow in a 'Pending KYC Upgrade' liability. The user is notified to upgrade. This is risk control implemented at the LEDGER level, where it's bulletproof, instead of in application code where every new code path is a new bypass.