The Net Stable Funding Ratio: How ASF, RSF and the 100% Minimum Shape a Bank's Structural Funding

What the Net Stable Funding Ratio Is Actually Measuring

The Net Stable Funding Ratio (NSFR) is one of two liquidity ratios that came out of Basel III. Most practitioners are more familiar with the Liquidity Coverage Ratio, and that familiarity can leave a blind spot. The LCR tells you whether you can survive a 30 day stress. The NSFR tells you whether your balance sheet is structurally sound over a one year horizon. Those are very different questions.

The NSFR measures whether your illiquid assets with longer tenors are funded by stable sources of funding. The ratio itself is simple:

NSFR = Available Stable Funding (ASF) / Required Stable Funding (RSF)

The regulatory minimum is 100%. If you fall below it, you have a structural funding problem: your assets need more stable funding than you actually have.

What matters in practice is that the ratio is not about whether you have cash today. A bank can be perfectly solvent, hold adequate HQLA, pass its LCR, and still have a NSFR problem. That problem will not show up as a crisis tomorrow. It will show up over months, as wholesale funding with shorter tenors becomes harder and more expensive to roll, and as the options available to fix it narrow.

Why the LCR Alone Is Not Enough

The 2007 to 2008 crisis illustrated the failure mode clearly. Banks were funding assets with long tenors (mortgages, structured products, illiquid corporate loans) with wholesale paper maturing within days, overnight repos, and asset-backed commercial paper conduits. As long as that paper kept rolling, the model worked. When confidence broke, the rollover stopped and the maturity mismatch became fatal within days.

The LCR was designed to give a bank 30 days of survival in a severe stress. That matters, but it does not address the underlying structural problem. A bank could satisfy the LCR on day one and still face the same rollover cliff if wholesale markets stayed shut beyond a month.

The NSFR addresses that by looking at the full year horizon and asking a harder question: are the funding sources that support your illiquid assets actually stable enough to be relied on?

Available Stable Funding (ASF): How Liability Sources Are Weighted

ASF is calculated by applying a weight to each liability category. The weight reflects how reliably that funding will remain with the bank under stress over a one year period. The calibration draws on observed behaviour in past crises.

The main categories and their weights are:

• Tier 1 capital and instruments with residual maturity of one year or more: 100%
• Stable retail deposits (insured, established relationship): 95%
• Less stable retail deposits and less stable qualifying small business deposits: 90%
• Wholesale funding from corporates outside the financial sector, sovereigns, and public sector entities with residual maturity of less than one year: 50%
• Other wholesale funding with residual maturity of less than one year, including most interbank deposits: 0%

The 0% on wholesale funding maturing within the year is the key tension. If you are funding yourself in overnight or very short dated wholesale markets, that funding does not contribute to your ASF at all. It is treated as if it could disappear tomorrow, because in a stress, it can.

Retail deposits get high weights precisely because the empirical evidence from crises shows they stay put. Insured deposits in particular have very low run off rates even under significant stress. That observation underpins both the NSFR ASF weights and the LCR run off factors.

Required Stable Funding (RSF): How Your Assets Drive the Denominator

RSF assigns a weight to each asset based on how much stable funding that asset requires. The logic is: the more illiquid an asset is, the more stable the funding behind it needs to be.

Key categories (simplified for illustration; the Basel III framework specifies distinct factors within these broad groupings):

• Central bank reserves: 0%
• Unencumbered Level 1 HQLA other than central bank reserves (for example, highest quality sovereign debt): 5%
• Unencumbered Level 2A assets: 15%
• Unencumbered Level 2B assets: 50%
• Qualifying residential mortgages with residual maturity of one year or more: 65%
• Other retail and SME loans with residual maturity of one year or more: 85%
• Corporate loans to counterparties outside the financial sector with residual maturity of less than one year: 50%
• Corporate loans to counterparties outside the financial sector with residual maturity of one year or more: 65%
• Encumbered assets: typically 100%, because you cannot use them to raise liquidity

The 0% on central bank reserves and the 5% on Level 1 sovereign debt reflect the fact that these assets are the most liquid in the system. They can be monetised quickly and reliably, so they require very little stable funding behind them. A 30 year mortgage at 65% sits at the opposite end: you cannot sell it quickly in a stress, so for every £1 of mortgage assets, £0.65 must be backed by stable funding.

An Illustrative Calculation

Take a simplified bank balance sheet. All numbers are illustrative.

Liabilities:

• Tier 1 equity: £500m (ASF weight 100%) = £500m ASF
• Debt maturing beyond one year: £300m (100%) = £300m ASF
• Stable retail deposits: £800m (95%) = £760m ASF
• Less stable retail deposits: £200m (90%) = £180m ASF
• Wholesale funding from corporates outside the financial sector with residual maturity of less than one year: £400m (50%) = £200m ASF
• Overnight interbank borrowing: £300m (0%) = £0m ASF

Total ASF: £1,940m

Assets:

• Central bank reserves: £200m (0%) = £0m RSF
• Level 1 sovereign bonds (unencumbered): £300m (5%) = £15m RSF
• Residential mortgages: £1,200m (65%) = £780m RSF
• Corporate loans with residual maturity of less than one year: £400m (50%) = £200m RSF
• Corporate loans with residual maturity of one year or more: £500m (65%) = £325m RSF
• Encumbered assets (posted as repo collateral): £100m (100%) = £100m RSF

Total RSF: £1,420m

NSFR = £1,940m / £1,420m = 136.6%

This bank passes comfortably. Now suppose it replaces £400m of stable retail deposits with an additional £400m of overnight interbank borrowing. ASF falls by £380m (the retail deposits were contributing £380m to ASF; the overnight interbank contributes £0m). Total ASF drops to £1,560m. RSF stays at £1,420m. NSFR is now £1,560m / £1,420m = 109.9%. Still passing, but the buffer has narrowed sharply. One more shift in the funding mix and you are approaching the minimum.

That arithmetic is exactly the intuition regulators wanted to embed. The ratio penalises wholesale funding with very short tenors structurally, not just in a stress scenario.

NSFR, FTP and Balance Sheet Incentives

The NSFR does not exist in isolation. It connects directly to Funds Transfer Pricing, and understanding that connection matters if you want the ratio to drive the right behaviour across the business.

FTP is the mechanism by which the treasury function allocates the cost and benefit of funding to business lines. A mortgage book with a high RSF weight consumes stable funding. A retail deposit with a high ASF weight provides it. If your FTP framework prices those accurately, the mortgage business pays more when it adds illiquid assets with longer tenors, and the retail banking team is rewarded for gathering sticky deposits.

If FTP does not reflect NSFR logic, you get the opposite incentives. A lending team that is not charged for the structural funding cost of a loan with a long tenor has no reason to care about the ratio. It will optimise for margin and leave the structural funding problem to the treasury function to solve after the fact.

Getting this alignment right is a judgement call that varies by institution. The exact implementation depends on your FTP methodology, your balance sheet composition, and how much granularity you want to push down to business level. But the underlying principle is consistent: the same stability logic that drives ASF and RSF weights should inform the prices you charge and pay internally for funding.

What the Ratio Tells a Treasury Team in Practice

A NSFR breach cannot be fixed with overnight liquidity management. You cannot borrow more in the repo market or sell some HQLA and solve it. Every tool that the daily liquidity desk uses operates within the LCR framework. The NSFR operates at a different level.

The distinction matters because the remedies available to fix a structural funding gap are slow and capital intensive. To move the ratio in a meaningful way, you generally need one or more of the following:

• Extending the tenor of your wholesale funding so more of it qualifies for higher ASF weights
• Growing your retail deposit base, particularly stable, insured deposits
• Issuing instruments with longer tenors (covered bonds, senior unsecured debt, Tier 2)
• Shrinking or repricing illiquid assets with longer tenors on the lending side
• Reducing encumbrance so fewer assets attract 100% RSF

Each of those actions takes months at minimum. Most take longer. That is why NSFR pressure is a board and senior management concern rather than a daily treasury problem. By the time it becomes urgent, the options have already narrowed.

The NSFR shapes funding strategy, FTP design, and balance sheet composition over a multi-year horizon. It deserves the same analytical attention as the LCR. If you want to go deeper on the liquidity management framework as a whole, the full Liquidity Management course is available on the Academy. Browse the current catalogue at theindustryportal.com/catalogue.