You have a ₦1,000,000 loan book. Industry experience says ~3% of loans default. Bad-debt write-off (Lesson 16) is reactive, when a specific loan turns bad, you write it off. Provisioning is PROACTIVE, you set aside a reserve today for losses you EXPECT to happen, before any specific loan defaults. This is the difference between honest financial reporting and discovering ugly surprises at year-end audit. IFRS 9 and US CECL both mandate forward-looking provisioning for any serious lender.