Interest income
Interest income is the interest a lender earns on loans it has made. For one loan, it is the interest earned on that loan; for a book, it is the interest earned across its loans. Lenders read it alongside credit losses and the cost of funding.
Example
Suppose a lender keeps a $1,000 loan outstanding for a year at 10% annual interest. As a simplified illustration, it earns $100 in interest income on that loan; the lender can compare its book’s interest income with credit losses and funding costs.
How lenders calculate interest income
Start with the principal outstanding during the period. For a simple estimate, multiply that balance by the annual rate and by the fraction of a year covered. For example, $8,000 outstanding for three months at 12% produces $240 of interest: $8,000 × 0.12 × 3/12. This is an illustration, not a market figure.
If repayments or rate changes alter the balance during the loan, calculate each period on the amount outstanding then and add the results. For a book, sum the interest recognized on each loan in the reporting period. A simple average balance multiplied by one rate can miss differences in repayment timing and loan terms.
Interest income, fees, funding costs and losses
Interest income is measured before the lender’s funding expense. Net interest income subtracts interest expense on funding from interest income for the same period. Interest income can rise even as net interest income falls if funding expense rises faster.
Fee income comes from fees charged to borrowers, rather than interest on outstanding principal. Its recognition can follow different accounting treatment from interest.
Neither measure alone shows lending profitability. Read interest income alongside credit losses, since losses can absorb much of the income.
Questions we get asked
Is interest income the same as cash interest received?
No. Interest income is recognized as it is earned over the loan’s life, so the amount recognized in a period can differ from the cash collected in that period. The timing depends on payment terms and applicable accounting treatment.
Does repayment of principal count as interest income?
No. Principal repayment returns part of the amount lent, whereas interest is earned on the outstanding balance. As principal falls, later interest generally accrues on a smaller balance, subject to the loan terms.
Can I compare interest income across lenders directly?
Only with context. Totals depend on book size, outstanding balances, rates and the period measured. Compare the same period, and consider funding costs and credit losses too.
What are examples of interest income for a lender?
Examples include interest on an instalment loan, a credit card balance carried past its grace period, an overdraft, and a business loan. Each is interest income for the lender as it is earned.
What is the interest income formula?
For a simple period, interest income = principal outstanding × annual interest rate × fraction of the year in the period. For an amortising loan, calculate each period using its outstanding balance, then add the amounts.
What is credit interest income?
For a lender, credit interest income is interest earned on the credit it extends. On a personal bank statement, “credit interest” is interest the bank pays into the account, so it is income for the account holder.
Is interest income revenue for a lender?
Yes, interest income is revenue for a lender and is usually its main revenue line. It is reported before interest expense, and fees are reported separately as fee income.
Decisimo’s loan profitability calculator shows the profit of one installment loan after losses and costs, including funding and acquisition, plus the default rate at which it breaks even.
