Glossary term
Net Interest Income
Net interest income is interest income earned on loans and securities minus interest expense paid on deposits and other funding.
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What Is Net Interest Income?
Net interest income, or NII, is interest income earned on loans, securities, and other interest-earning assets minus interest expense paid on deposits, borrowings, and other funding. It is one of the most important revenue sources for banks and lenders.
NII measures the dollar profit from the basic maturity and credit intermediation business: gathering funding and investing or lending it at a higher yield. It is related to net interest margin, but not the same. NII is a dollar amount; net interest margin scales that amount against earning assets.
Key Takeaways
- Net interest income equals interest income minus interest expense.
- It is a core earnings driver for banks, credit unions, mortgage lenders, and other financial institutions.
- NII rises or falls with loan yields, securities yields, deposit costs, borrowing costs, balance-sheet size, and asset mix.
- It should be analyzed with credit losses, noninterest income, funding stability, and interest-rate risk.
- NII is a dollar measure, while net interest margin is a percentage measure.
Net Interest Income Formula
The basic formula is:
Interest income may come from loans, leases, securities, cash balances, and other interest-earning assets. Interest expense may come from deposits, Federal Home Loan Bank advances, repurchase agreements, long-term debt, and other borrowings.
What Drives NII
NII depends on both rates and volumes. A bank can grow NII by expanding loans, buying higher-yielding assets, improving loan pricing, or lowering funding costs. It can lose NII if deposit costs rise, borrowers refinance, credit demand falls, or low-yielding securities remain on the balance sheet while funding costs reset higher.
Asset and liability timing matters. If a bank's assets reprice slowly but deposits reprice quickly, NII can compress in a rising-rate environment. If asset yields adjust faster than funding costs, NII may expand. This is why banks discuss balance-sheet sensitivity and deposit behavior in earnings reports.
NII Versus NIM
Metric | Form | What it answers |
|---|---|---|
Net interest income | Dollar amount | How much spread income did the institution earn? |
Net interest margin | Percentage | How efficiently did earning assets produce spread income? |
Noninterest income | Dollar amount | How much revenue came from fees or other noninterest sources? |
Investor Context
For a bank investor, NII is central but incomplete. Strong NII can be offset by credit losses, higher provisions, weak fee income, operating expenses, or capital pressure. A bank may also increase NII by taking more risk, such as reaching for yield or growing loans too aggressively.
Analysts therefore compare NII with net interest margin, loan growth, deposit trends, securities duration, credit quality, allowance levels, and capital ratios. The best NII growth is durable, funded by stable deposits, and supported by sound credit underwriting.
Rate Sensitivity
NII can be asset sensitive or liability sensitive depending on how quickly assets and funding reprice. An asset-sensitive bank may benefit when rates rise because loan and securities yields adjust faster than deposit and borrowing costs. A liability-sensitive bank may see NII pressured when funding costs rise more quickly.
Management teams often disclose interest-rate sensitivity scenarios to show how projected NII might change under different rate paths. Those disclosures are estimates, not guarantees, because customer behavior, deposit competition, prepayments, and loan demand can shift.
Quality of NII Growth
Healthy NII growth usually comes from a sound combination of loan demand, disciplined pricing, stable deposits, and manageable credit risk. Weaker growth can come from stretching for yield, extending duration too far, or expanding into riskier borrowers without adequate reserves.
That is why bank earnings analysis rarely stops at NII. The same balance sheet that produces interest income also carries credit, liquidity, and duration risk.
The Bottom Line
Net interest income is the spread income a financial institution earns after subtracting funding costs from interest income. It is a core banking profit measure, but it must be read with margin, risk, credit quality, and the balance-sheet structure that produced it.