The liquidity buffer · RiskAtoms Academy

By the end you will be able to

1Build a liquidity buffer from a bank's holdings: HQLA levels, haircuts and what is left out because it is encumbered.
2Apply the 40% cap on Level 2 assets and the 15% cap on Level 2B, and derive them from the shares of the stock.
3Check holdings against the operational requirements: unencumbered, under treasury's control, tested, diversified.
4Explain encumbrance and pre-positioned collateral, and how a buffer is turned into cash in a stress.

Why it matters

RiskAtoms Bank owns £67bn of assets, and in the combined stress of L3.5.05: Liquidity stress tests and survival horizons it lasts 47 days on just £13.89bn of them. Not a pound of its £30bn of mortgages helps, because nobody buys a mortgage book in a week. The buffer is the small slice of the balance sheet that can become cash on demand. Which assets qualify, how much each one counts, and whether it is really free to use are the difference between a buffer on paper and cash on the day.

Core explanation

What counts, and how much

Illustrative dataRiskAtoms Bank plc's liquidity book

A £67bn balance sheet on one made-up reporting date, in pounds: every line's contractual maturity, its HQLA level, LCR rate and NSFR factors, the undrawn facilities and collateral triggers, and a daily 90-day stress test in three scenarios. The numbers are round illustrative values, not any bank's data, and the cash flows are principal only (no interest). The same book runs through every lesson in Module 3.5, so the figures agree.

This lesson uses the book's HQLA lines, encumbered and pre-positioned assets. The caps are applied without unwinding the short-term repo, a simplification the Basel text does not make.

The liquidity buffer is the bank's stock of high-quality liquid assets (HQLA): the numerator of the LCR named in L2.7.04: Basel III and its finalisation, and the counterbalancing capacity of the stress test. An asset is liquid in a stress if it is simple, easy to value, traded in a deep market and accepted by central banks: the market liquidity of L3.2.17: Market liquidity risk, judged for the worst week, not an ordinary one. The Basel LCR text sorts HQLA into three levels (LCR30.40 to 30.45):

Level	Examples	Haircut	Limit
Level 1	Cash, central bank reserves (as far as they can be drawn in stress), 0% risk-weight government bonds	0%	None
Level 2A	20% risk-weight government bonds; corporate and covered bonds rated AA− or better	15%	Level 2 ≤ 40%
Level 2B	AA residential MBS (25%); corporate bonds BBB− to A+ (50%); shares in a major index (50%)	25–50%	Level 2B ≤ 15%

The haircut is the share of market value that does not count. Unsecured bonds of banks and other financial firms, and the bank's own covered bonds, are left out of Level 2 entirely: in a crisis they fall with the banking system. Here is the book's buffer:

Holding	Level	Held	Encumbered	Free	Haircut	In the buffer
Cash and central bank reserves	Level 1	£6.0bn	–	£6.0bn	0%	£6.00bn
UK government bonds (gilts)	Level 1	£7.0bn	£1.5bn	£5.5bn	0%	£5.50bn
Covered bonds and AA corporate bonds (Level 2A)	Level 2A	£2.0bn	–	£2.0bn	15%	£1.70bn
BBB corporate bonds and listed shares (Level 2B)	Level 2B	£1.0bn	–	£1.0bn	50%	£0.50bn
Stock of HQLA						£13.70bn

Level 2 is 16.1% of the stock and Level 2B 3.6%, well inside the caps. The bank could add £3.66bn of Level 2B (at market value) before the 15% cap bit.

Free to use: the operational requirements

Owning an asset is not enough. To count, it must pass the operational tests of LCR30.13 to 30.20:

Unencumbered: not pledged to back any trade, and free of legal or operational limits on selling it (30.16).
Under control: held by the function that manages liquidity, usually treasury, with the authority and the means to sell it at any time (30.18).
Tested: part of it sold or repoed from time to time to prove the market and the processes work (30.15).
Monetisable: the bank has the operational capability to turn it into cash in time (30.17). If it hedges the assets, it counts the cost of closing the hedge (30.19).
Diversified within each asset class, apart from home sovereign debt and central bank reserves (30.29).

Sort itIn the buffer or not?

Each item is a holding of RiskAtoms Bank. Does it count in the stock of HQLA?

£6bn of reserves at the Bank of England, which the bank may draw down in a stress.
£1.5bn of gilts pledged to repo lenders for the next three weeks.
Gilts placed with the central bank in advance and not used to borrow.
Covered bonds RiskAtoms Bank issued itself and bought back.
Gilts held by the trading desk to hedge a swap book, outside treasury's control.
£6bn of mortgages pre-positioned at the central bank.

Encumbrance

An encumbered asset is spoken for. RiskAtoms Bank has pledged £6.5bn of assets, 9.7% of its balance sheet:

Asset	Pledged against	Amount
Gilts	Repo funding (under 30 days)	£1.5bn
Residential mortgages	Covered bond pool	£3.5bn
Residential mortgages	Central bank term funding	£1.5bn
Total encumbered		£6.5bn

The covered bond pool is 40% larger than the £2.5bn of bonds it backs (over-collateralisation). Encumbrance matters twice. Every pledged pound is a pound unsecured creditors and depositors cannot reach if the bank fails. And it creeps up in a stress: as unsecured lenders leave, the bank borrows secured instead, pledging more, while falling collateral values and downgrade triggers (L3.4.05: Collateral and the CSA) demand still more.

Pre-positioned collateral

The bank has also placed £6.0bn of mortgages with the central bank (pre-positioned) but not borrowed against them. With the central bank's 30% haircut that is £4.2bn it could borrow at short notice. Mortgages are not HQLA, so none of it is in the LCR. But it is real capacity: added to the combined stress, it turns a −£2.96bn shortfall on day 90 into £1.24bn of headroom, and the bank survives past day 90 instead of 47 days. Pre-positioning takes months, so it has to be done before the stress; whether and when to draw on it is a question for the contingency funding plan (L3.5.10: Contingency funding plans).

Monetising the buffer

ExploreFour ways to turn the buffer into cash

Click each route to see how fast it is and what it costs.

Use cash

Reserves at the central bank pay outflows directly, the same day. RiskAtoms Bank holds £6.0bn. The book treats all of it as usable, which assumes no minimum reserve the bank must keep.

The LCR haircuts are fixed by the rule; the stress test uses the bank's own estimate of forced-sale discounts. For this book the stress values are slightly higher:

Holding	Free	LCR value	Combined-stress value
Cash and central bank reserves	£6.0bn	£6.00bn	£6.00bn
UK government bonds (gilts)	£5.5bn	£5.50bn	£5.39bn
Covered bonds and AA corporate bonds (Level 2A)	£2.0bn	£1.70bn	£1.80bn
BBB corporate bonds and listed shares (Level 2B)	£1.0bn	£0.50bn	£0.70bn
Total	£14.5bn	£13.70bn	£13.89bn

The formal version

Write $L_1, L_{2A}, L_{2B}$ for each level after haircuts and $S = L_1 + L_{2A} + L_{2B}$ for the stock. The two caps are shares of the stock, and they turn into limits relative to Level 1:

\begin{aligned} L_{2A} + L_{2B} \le 0.40\,S &\iff 0.60\,(L_{2A} + L_{2B}) \le 0.40\,L_1 \iff L_{2A} + L_{2B} \le \tfrac{2}{3}\,L_1 \\ L_{2B} \le 0.15\,S &\iff 0.85\,L_{2B} \le 0.15\,(L_1 + L_{2A}) \iff L_{2B} \le \tfrac{15}{85}\,(L_1 + L_{2A}) \\ \text{if the 40\% cap binds, } S = L_1 / 0.6: \quad L_{2B} \le 0.15 \times \tfrac{L_1}{0.6} &= \tfrac{15}{60}\,L_1 \end{aligned}

Anything above the limits is excess, taken off the stock (LCR30.35 to 30.39):

\begin{aligned} E_{2B} &= \max\!\left(L_{2B} - \tfrac{15}{85}(L_1 + L_{2A}),\ L_{2B} - \tfrac{15}{60}L_1,\ 0\right) \\ E_{2} &= \max\!\left(L_{2A} + L_{2B} - E_{2B} - \tfrac{2}{3}L_1,\ 0\right) \\ \text{HQLA} &= L_1 + L_{2A} + L_{2B} - E_{2B} - E_2 \end{aligned}

In the Basel text these are “adjusted” amounts: short-term repos, reverse repos and collateral swaps maturing within 30 days are unwound first, so a bank cannot dodge a cap by swapping Level 2B for Level 1 for a few days (LCR30.34, 30.37). The book skips that step.

Try it

The sliders start at the book's unencumbered holdings. Push Level 2B up and watch the 15% cap start to bite; then cut Level 1 and see both caps bind.

Try itBuild the buffer

Level 1 (cash, gilts)£11.5bn

Level 2A (AA bonds)£2.00bn

Level 2B (BBB bonds, shares)£1.00bn

Level 1, no haircut£11.50bn
Level 2A after 15% haircut£1.70bn
Level 2B after 50% haircut£0.50bn
Before the caps£13.70bn

Stock of HQLA£13.70bn

LCR on the book's outflows157.4%

Excess Level 2B (15% cap)£0.00bn

Excess Level 2 (40% cap)£0.00bn

Level 2 share before caps16.1%

Level 2B share before caps3.6%

Lost to haircuts and caps£0.80bn

No cap binds. Push Level 2B past about 15% of the stock, or Level 2 past 40%, and watch the excess appear. Holdings are unencumbered market values. The caps here ignore the unwinding of short-term secured trades.

Worked example

The book's buffer, and a yield-chasing swap

From holdings to the stock of HQLA

Step 1 of 5

1
Take out what is pledged
$\begin{aligned} L_1 &= \underbrace{\text{£}6{,}000\text{m}}_{\text{reserves}} + \underbrace{\text{£}7{,}000\text{m} - \text{£}1{,}500\text{m}}_{\text{gilts not in repo}} = \text{£}11{,}500\text{m} \end{aligned}$

Book figures: LCR before the swap 157.4%, net cash outflows £8,705m.

Regulatory lens

The definitions, haircuts, caps and operational requirements on this page are from the Basel Framework's LCR30. The buffer is meant to be used: the Basel text says that in a stress it is “entirely appropriate” for banks to use their HQLA and fall below 100% (LCR20.5). How the ratios are managed day to day is in L3.5.07: LCR and NSFR in practice; national versions of the rules, and how supervisors respond when a bank uses its buffer, are in M4.5: Liquidity and IRRBB regulation.

Spark Atoms

Spark AtomA year to get ready

Before the Bank of England will lend against a pool of loans it reviews the data, the processes and the legal documents. Its guide to pre-positioning puts the legal review alone at 6 to 12 months; once a pool is eligible, moving it into the pool that backs lending can be done the next working day.

Spark AtomShares can be HQLA

Level 2B includes ordinary shares, at a 50% haircut, but only if they are exchange-traded, centrally cleared and in a major stock index of the bank's home jurisdiction (LCR30.45). Shares of banks and other financial firms are left out.

Key takeaways

The buffer is unencumbered HQLA after haircuts: Level 1 at 100%, Level 2A at 85%, Level 2B at 50 to 75%. The book's is £13.7bn.
Level 2 may be at most 40% of the stock and Level 2B at most 15%: limits of 2/3 of Level 1, and of 15/85 of Level 1 plus 2A.
To count, assets must be unencumbered, under treasury's control, tested by periodic sale or repo, and diversified.
Encumbrance (9.7% of the book) shrinks what is free and tends to rise in a stress.
Pre-positioned loans are not HQLA but are real capacity: £4.2bn for the book, enough to carry the combined stress past 90 days.
Chasing yield in Level 2B costs buffer twice, through the haircut and the cap: a £5.0bn swap costs £4.05bn.

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Glossary

Liquidity buffer: The stock of unencumbered, high-quality liquid assets a bank holds to meet outflows in a stress without help.
High-quality liquid assets (HQLA): High-quality liquid assets: cash, central bank reserves and securities that can be turned into cash quickly, with little loss, even in a stress.
Level 1 assets: The best HQLA: cash, central bank reserves that can be drawn in stress, and top-rated government securities. No haircut, no limit.
Level 2A assets: Good HQLA with a 15% haircut: for example AA- or better corporate and covered bonds, and 20% risk-weight government securities.
Level 2B assets: Lower-quality HQLA with a 25% or 50% haircut: AA residential MBS, BBB- or better corporate bonds, shares in a major index.
Haircut: The share of an asset's market value that does not count in the buffer, because it might not be realised in a stress.
Encumbered asset: Pledged or otherwise tied up: an asset that backs a repo, a covered bond or a central bank loan cannot be sold or pledged again.
Over-collateralisation: Collateral in excess of the debt it backs: a cover pool larger than the covered bonds outstanding.
Pre-positioned collateral: Collateral, often loans, placed with the central bank in advance so the bank can borrow against it at short notice.
Monetise: Turn an asset into cash, by repo, by outright sale or by borrowing from the central bank.

Deep Dives & Origins

Deep Dives

Basel Committee on Banking Supervision, Basel Framework, LCR30 High-quality liquid assets, BIS. Intermediate.
Bank of England, Guide to Pre-positioning Loan Collateral. Intermediate.

Origins

Basel Committee on Banking Supervision, Basel Framework, LCR30 High-quality liquid assets, paragraphs 30.10, 30.13 to 30.20, 30.29, 30.33 to 30.45, BIS, version effective 15 December 2019.
Basel Committee on Banking Supervision, Basel Framework, LCR20 Calculation, paragraph 20.5, BIS.
Bank of England, Guide to Pre-positioning Loan Collateral, Bank of England, last updated 15 July 2026.
Bank of England, Independent Evaluation Office, Evaluation of the Bank of England's approach to providing sterling liquidity, January 2018 (on the stigma of using the Discount Window Facility).
Commission Implementing Regulation (EU) 2015/79, Annex XVII (asset encumbrance reporting), paragraph 11 (definition of encumbrance).

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