A comprehensive explainer of IRRBB — covering the regulatory framework, EVE and NII measures, the six shock scenarios, repricing gap analysis, the standardised framework, the Supervisory Outlier Test, and the Irish bank context.
Interest Rate Risk in the Banking Book (IRRBB) is the risk that changes in market interest rates will adversely affect either the economic value of a bank's balance sheet or its net interest income. It is one of the most material risks facing Irish banks given their large tracker mortgage books, growing fixed-rate lending, and sensitivity to ECB rate decisions.
Banks borrow short (deposits, wholesale funding) and lend long (mortgages, term loans). When interest rates change, the value and cashflows of assets and liabilities move differently — creating a mismatch that affects both the economic value of the bank and its ongoing earnings.
Regulators require banks to measure IRRBB through two lenses: EVE (Economic Value of Equity) — a balance sheet / capital measure capturing the long-run present value impact; and NII (Net Interest Income) — an earnings measure capturing the short-term income impact over a 1–2 year horizon.
Irish banks carry a legacy stock of tracker mortgages whose rate moves automatically with the ECB Main Refinancing Rate. This creates a direct, mechanical link between ECB rate decisions and bank NII — a feature that dominated Irish bank IRRBB management through the 2022–2024 rate cycle.
| Component | Description | Main Driver | Irish Relevance |
|---|---|---|---|
| Repricing Risk | Risk from differences in the timing of rate changes on assets vs. liabilities. The most common form. | Maturity / repricing date mismatch between loans and deposits | Very high — tracker mortgages reprice instantly with ECB; fixed-rate deposits reprice at maturity |
| Yield Curve Risk | Risk from changes in the shape of the yield curve (steepening, flattening, inversion) affecting differently dated instruments. | Mismatch in duration between long-dated assets and short-dated liabilities | High — long-dated fixed mortgages funded by short deposits create yield curve exposure |
| Basis Risk | Risk from changes in the spread between different rate indices (e.g. EURIBOR vs. ECB MRR) that affect differently priced instruments. | Assets and liabilities priced off different reference rates | Significant — tracker mortgages (ECB MRR) vs. wholesale funding (EURIBOR) creates basis exposure |
| Optionality Risk | Risk from embedded options in banking products — prepayment options in mortgages, withdrawal rights in deposits, interest rate caps/floors. | Customer behaviour changes driven by rate movements | Material — Irish mortgage prepayment behaviour and early deposit withdrawal in rising rate environment |
The IRRBB regulatory framework has evolved substantially since the 2008 financial crisis. The current regime is built on BCBS 368, implemented in the EU through EBA Guidelines and, from 2025, embedded in binding law through CRR III.
| Instrument | Issued | Key Requirement | Status |
|---|---|---|---|
| BCBS 368 | April 2016 | Basel Committee standard setting out principles for IRRBB management, measurement, and disclosure. Defines the six standard interest rate shock scenarios and the EVE/NII framework. | International standard |
| EBA GL/2018/02 | July 2018 | EBA Guidelines on the management of interest rate risk arising from non-trading book activities. EU implementation of BCBS 368. Mandates EVE and NII measurement, six shock scenarios, and the Supervisory Outlier Test. | Binding for SSM banks |
| CRD V / CRR II | 2019–2021 | Embedded IRRBB requirements in EU legislation. Required banks to notify competent authorities when EVE declines by more than 15% of Tier 1 capital under standardised shocks. | In force |
| EBA RTS on IRRBB | 2022 | Regulatory Technical Standards on the standardised and simplified standardised approaches for IRRBB, implementing CRR III Article 84 requirements including NII outlier test (2.5% of total assets). | CRR III phased in 2025 |
| CRR III Art. 84 | 2025 | Binding law implementing the standardised approach for IRRBB. Introduces the NII Supervisory Outlier Test (SOT) at 2.5% of total assets alongside the existing 15% EVE SOT. Banks failing either test face automatic supervisory consequences. | Phasing in 2025 |
Banks may use their own models to measure IRRBB, subject to ECB supervisory review. Internal models can capture bank-specific behavioural assumptions (e.g. actual Irish mortgage prepayment rates, actual deposit stability) more accurately than the standardised approach.
Under CRR III, all banks must be able to calculate IRRBB under the standardised approach, even if they primarily use internal models. The standardised approach uses prescribed behavioural assumptions for NMDs, prepayments, and automatic interest rate options — removing much bank discretion.
EVE is the present value of all future cashflows from assets minus the present value of all future cashflows from liabilities. It represents the economic value of the bank's equity — the residual if all positions were run off at current market rates. IRRBB EVE sensitivity measures how this economic value changes when interest rates shift.
Most banks are liability-sensitive at the short end and asset-sensitive at the long end. A rate rise has different effects on different parts of the balance sheet:
Long-dated fixed-rate assets (mortgages, bonds) fall in value when rates rise — the discount rate increases, reducing the PV of future cashflows. A 25-year fixed mortgage originated at 2% is worth significantly less when market rates are 4%.
Short-dated liabilities (demand deposits, short-term funding) also fall in value when rates rise, but less so because they mature sooner and the discount rate effect is smaller. This liability gain partially offsets the asset loss.
Simplified EVE sensitivity calculator. Adjust asset and liability characteristics to see the net EVE impact of a rate shock. Uses modified duration as the sensitivity measure.
NII sensitivity measures how a bank's net interest income — the difference between interest earned on assets and interest paid on liabilities — changes over a forward-looking period (typically 1 year) when interest rates shift. It is a short-term earnings measure, complementing the long-run balance sheet focus of EVE.
For an Irish bank, the NII impact of a rate move depends on which parts of the book reprice and when:
| Product | Asset or Liability | Repricing Behaviour | NII Impact of +100bps |
|---|---|---|---|
| Tracker mortgages | Asset | Immediate — rate = ECB MRR + fixed margin. Full pass-through on next ECB decision date. | Positive — higher interest received |
| Variable rate mortgages | Asset | Bank discretion — typically passed through with a lag of 1–3 months at bank's discretion | Positive — subject to timing and competitive pressure |
| Fixed rate mortgages | Asset | No repricing until fixed term ends (2–10 years). NII unaffected during fixed period. | No impact during fixed period |
| Demand deposits (current accounts) | Liability | Bank discretion — in practice Irish banks were very slow to pass on rate rises to deposit customers in 2022–2024 | Positive (for bank) — lower cost if not passed on |
| Fixed term deposits | Liability | No repricing until maturity. Rate fixed for the term (1–5 years typically) | No impact until maturity |
| Wholesale / interbank funding | Liability | Typically EURIBOR-linked — reprices with market rates. Short-dated rollover funding reprices immediately. | Negative — higher funding cost |
BCBS 368 and EBA GL/2018/02 define six standard interest rate shock scenarios that all banks must apply to their IRRBB measurement. The shocks are defined as instantaneous parallel and non-parallel shifts in the risk-free yield curve. EVE must be calculated under all six; NII under the two parallel shocks.
| Scenario | EVE Impact (typical) | NII Impact (typical) | Irish Priority |
|---|---|---|---|
| Parallel Up +200bps | Negative (long assets lose value) | Positive (trackers reprice up) | High — SOT risk on EVE; NII windfall |
| Parallel Down −200bps | Positive (long assets gain value) | Negative (trackers reprice down) | High — NII floor risk; ECB rate floor constraint |
| Short Rate Up +250bps | Modest negative | Very positive (trackers only) | Critical — isolates tracker book benefit |
| Short Rate Down −250bps | Modest positive | Very negative (trackers only) | Critical — isolates tracker book risk |
| Steepener | Mixed — depends on book structure | Complex interaction | Moderate |
| Flattener | Mixed — depends on hedging | Funding cost focused | Moderate |
A repricing gap report shows the difference between assets and liabilities that reprice within each time bucket — revealing where the bank is over- or under-hedged across the maturity spectrum. A positive gap (assets > liabilities) benefits from rate rises; a negative gap is hurt by them.
EBA GL/2018/02 requires repricing gap analysis across standardised time buckets. Each instrument is placed in the bucket corresponding to its next repricing date — not its final maturity. A 20-year tracker mortgage reprices today (overnight bucket) because its rate changes with every ECB decision.
| Time Bucket | Repricing Assets (€bn) | Repricing Liabilities (€bn) | Gap (€bn) | Cumulative Gap (€bn) | Interpretation |
|---|---|---|---|---|---|
| Overnight / Floating | 12.0 | 8.5 | +3.5 | +3.5 | Asset-sensitive at short end — trackers + variable rate assets exceed floating-rate liabilities |
| ≤ 1 month | 2.5 | 4.0 | −1.5 | +2.0 | Short-dated wholesale funding exceeds maturing short assets |
| 1–3 months | 1.8 | 2.8 | −1.0 | +1.0 | Continued liability pressure from rolling wholesale |
| 3–6 months | 2.2 | 1.8 | +0.4 | +1.4 | Fixed mortgages beginning to roll off and reprice |
| 6–12 months | 3.0 | 3.5 | −0.5 | +0.9 | Term deposit maturities create liability repricing |
| 1–2 years | 4.5 | 3.0 | +1.5 | +2.4 | Fixed-rate mortgages with 1–2yr terms roll off |
| 2–5 years | 5.0 | 2.5 | +2.5 | +4.9 | Larger fixed-rate asset block repricing |
| > 5 years | 8.0 | 4.0 | +4.0 | +8.9 | Long-duration fixed assets; equity and perpetual instruments |
Demand deposits (current accounts, savings accounts with no fixed term) have no contractual maturity — customers can withdraw at any time. But in practice, a proportion of these deposits is stable and acts like long-term funding. Banks must model this behavioural stability.
The portion of demand deposits that is historically stable regardless of rate environment — modelled as long-term funding (up to a cap of 5 years average maturity under EBA guidelines). This portion reduces interest rate sensitivity because it is treated as fixed-rate long funding rather than instant repricing.
The volatile portion of demand deposits — particularly transaction balances and large corporate deposits — that may be withdrawn or repriced quickly in a rising rate environment. Modelled as short-term (overnight or 1-month) funding. The size of this portion grew substantially in Ireland during the 2022–2024 rate cycle as customers actively searched for yield.
Under CRR III and EBA RTS, banks must be able to measure IRRBB using the standardised approach — a prescribed methodology with supervisory assumptions for behavioural parameters. Even banks using internal models must calculate the standardised approach result for comparison purposes.
| Parameter | Standardised Assumption | Internal Model Alternative | Irish Bank Impact |
|---|---|---|---|
| NMD average maturity — retail | Maximum 4.5 years weighted average; 5 year cap per tranche | Own behavioural model based on historical deposit data | Internal models typically justify longer assumed maturities for sticky Irish retail deposits — reduces EVE sensitivity vs. standardised |
| NMD average maturity — wholesale | Maximum 4.5 years weighted average; shorter caps for financial customers | Own model — typically shorter than retail | Corporate deposits assumed more rate-sensitive; shorter modelled maturity |
| NMD pass-through rate (repricing) | Prescribed by currency and customer type. EUR retail: low pass-through (deposits slow to reprice) | Own historical pass-through data — validated against observed behaviour | Irish banks' low actual pass-through in 2022–2024 broadly consistent with standardised assumptions |
| Loan prepayment rate | Prescribed conditional prepayment rates (CPR) by product type. Typically 10–20% CPR for residential mortgages. | Own prepayment model based on historical data and rate incentive | Irish mortgage prepayment rates historically low by European standards — own models may use lower CPR; extends effective duration of mortgage book |
| Automatic interest rate options | Prescribed delta for embedded floor/cap options. Fixed-rate mortgages have embedded prepayment options treated with prescribed deltas. | Own option-adjusted models | Tracker mortgage floor at 0% (ECB rate cannot go below zero for tracker purposes) is a key embedded option |
| Credit spread component | Excluded from IRRBB measurement — credit spread changes are CSRBB not IRRBB | Consistent — credit spread changes measured separately | Irish sovereign spread widening/tightening is CSRBB, not IRRBB, even where it affects bank asset values |
The Supervisory Outlier Tests (SOTs) are the regulatory tripwires that automatically trigger supervisory consequences when a bank's IRRBB sensitivity exceeds defined thresholds. There are two tests — one for EVE (capital-focused) and one for NII (earnings-focused), the latter introduced under CRR III.
A bank is an outlier if the decline in EVE under any of the six standard shock scenarios exceeds 15% of Tier 1 capital. The test uses the worst scenario across all six shocks (typically the parallel up or down shock).
Introduced under CRR III (from 2025). A bank is an outlier if the decline in NII over a 12-month horizon under either parallel shock exceeds 2.5% of total assets. This is a much more mechanical test than the EVE SOT.
Two illustrative Irish banking book scenarios — a tracker-heavy retail bank and a more balanced bank with a growing fixed-rate mortgage book — showing how IRRBB exposures are calculated, interpreted, and managed.
| Metric | Parallel Up +200bps | Parallel Down −200bps | Short Rate Up +250bps | Assessment |
|---|---|---|---|---|
| ΔEVE | −€1,750m | +€980m | −€420m | Long-duration fixed mortgages drive negative EVE in rising rate scenario |
| ΔEVE / Tier 1 | −41.7% | +23.3% | −10.0% | EVE SOT BREACHED under parallel up — supervisory notification required |
| ΔNII (12 month) | +€310m | −€290m | +€225m | Tracker book generates large NII uplift in rising rate scenario |
| ΔNII / Total Assets | +0.89% | −0.83% | +0.64% | NII SOT not breached — well within 2.5% threshold |
Hedging response — To reduce EVE sensitivity without giving up NII, the bank could:
Pay-fixed / receive-floating swaps convert fixed-rate mortgage duration into floating — reducing the duration gap and therefore EVE sensitivity. The swap generates a negative carry cost (paying fixed) but reduces EVE risk.
Issue longer-dated fixed rate bonds (covered bonds, senior preferred) to match the duration of fixed-rate assets. Reduces the duration mismatch directly. Irish banks have expanded covered bond programmes for exactly this purpose.
As tracker stock naturally amortises and new fixed-rate lending grows, the balance between instant-repricing trackers and long-duration fixed assets shifts — organically reducing the EVE sensitivity over time.
| Metric | Parallel Up +200bps | Parallel Down −200bps | Assessment |
|---|---|---|---|
| ΔEVE | −€1,950m | +€1,420m | Larger EVE sensitivity than Case A — longer average fixed mortgage duration (7yr vs. 5yr) |
| ΔEVE / Tier 1 | −65.0% | +47.3% | Severe EVE SOT breach — large fixed book with less NII buffer from trackers |
| ΔNII (12 month) | +€85m | −€95m | Much smaller NII uplift — fewer trackers mean less natural rate hedge on income |
| ΔNII / Total Assets | +0.34% | −0.38% | NII SOT comfortably passed |
IRRBB is uniquely important for Irish banks given the structural features of the Irish mortgage market — the legacy tracker book, rapid growth in fixed-rate lending, sticky retail deposits, and direct exposure to ECB rate decisions. The 2022–2024 rate cycle was the most significant IRRBB event in Irish banking since the crisis.
| Product | Rate Type | Repricing | IRRBB Effect | Approximate Stock (2024) |
|---|---|---|---|---|
| Tracker mortgages | Variable (ECB-linked) | Instantaneous — every ECB decision | Positive NII in rising rates; floored at ECB rate + spread | ~€20–25bn (AIB + BOI + PTSB combined) |
| Variable rate mortgages | Variable (bank SVR) | Bank discretion — typically 1–3 month lag | Positive NII; delayed pass-through limits immediacy | ~€10bn |
| Fixed rate mortgages (1–5yr) | Fixed | No repricing until end of fixed term | No NII impact during fixed term; long-duration EVE risk | ~€30bn — fastest growing segment |
| Fixed rate mortgages (>5yr) | Fixed | Long duration — 7–30 years | Very high EVE sensitivity; small in Ireland but growing | ~€5bn |
ECB raises rates from 0% for the first time since 2011. Irish tracker mortgages — priced at ECB MRR + a fixed spread — immediately reprice upward. Banks see instant NII uplift on their tracker books with no corresponding increase in deposit costs (Irish banks are very slow to pass ECB rate rises to retail depositors).
With ECB rates rising from 0% to 4% (450bps) and Irish retail deposit pass-through rates remaining below 20%, Irish banks experience a dramatic NII uplift. AIB and BOI report record NII levels. The structural position — large tracker books, sticky retail deposits — proves enormously valuable. NII Tab
As rates rise, the parallel-up shock scenario produces increasing ΔEVE losses. Fixed-rate mortgages originated at 2–3% rates are now discounted at 4–5% risk-free rates, reducing their present value significantly. Banks with large fixed-rate books begin to approach or breach the 15% EVE SOT. Pillar 3 disclosures show growing ΔEVE sensitivity at both pillar banks. EVE Tab
Both AIB and BOI expand their interest rate swap overlay programmes — paying fixed / receiving floating to reduce net duration. Covered bond issuance provides longer-dated fixed funding to match fixed-rate asset duration. ALCO frequency increases; Board-level oversight of IRRBB position intensifies. ECB supervisory dialogue on IRRBB risk management becomes more active.
ECB reverses course, cutting rates from 4% toward a neutral level. Tracker NII begins to fall automatically. Banks face the reverse scenario — NII headwind from tracker repricing down, EVE gain as fixed-rate assets appreciate. The NII SOT (introduced under CRR III) becomes more relevant as falling rates test downside NII resilience. SOT Tab
AIB carries the largest tracker mortgage stock of any Irish bank. This creates the greatest NII sensitivity to ECB rates — both positive (rising rates) and negative (falling rates). AIB uses a substantial interest rate swap portfolio to manage EVE sensitivity and discloses full IRRBB metrics under Pillar 3 each quarter. The ECB rate cut cycle from 2024 represents the key near-term NII headwind.
BOI's strategic shift toward fixed-rate mortgage lending (driven by customer demand and regulatory preferences) has materially changed its IRRBB profile — moving it from predominantly tracker-sensitive (short-term NII risk) toward fixed-rate duration risk (EVE-sensitive). BOI's UK book adds a sterling IRRBB dimension requiring separate management under PRA rules.
PTSB has the highest concentration of tracker mortgages relative to its balance sheet — legacy of the pre-crisis market position. This gives PTSB the most acute NII sensitivity to ECB rates. The tracker book has been a primary driver of PTSB's financial recovery — the 2022–2024 rate cycle produced exceptional NII for PTSB relative to its size. The rate cut cycle from 2024 is therefore a more significant NII headwind for PTSB than for peers.
| Connection | How IRRBB Links | Reference |
|---|---|---|
| Credit Risk / IRB | Rising interest rates increase PD on variable-rate borrowers (higher debt service costs). The rate shock scenarios used in IRRBB should be consistent with the macro scenarios used in IRB PD stress testing. A bank managing IRRBB must also consider the credit risk consequence of rate shocks on its borrower base. | IRB Explainer — PD Modelling |
| IFRS 9 / ECL | The macroeconomic scenarios used in IFRS 9 ECL (PiT PD, house price forecasts, unemployment) should be consistent with the rate paths implied by IRRBB shock scenarios. A parallel-up shock should translate into a downside macro scenario in IFRS 9 — higher rates → lower economic activity → higher PD → higher ECL provisions. | IFRS 9 Explainer — Macro Overlays |
| Liquidity Risk | IRRBB and liquidity risk are closely related — deposit outflows (a liquidity risk) change the bank's funding structure and therefore its IRRBB position. If rate rises trigger deposit outflows, the bank may need to replace stable long-term NMD funding with shorter wholesale funding — increasing both liquidity risk and IRRBB sensitivity simultaneously. | ILAAP / LCR Framework |
| Capital (ICAAP / SREP) | IRRBB EVE sensitivity feeds directly into the ICAAP as a Pillar 2 capital requirement. Banks must hold sufficient capital to absorb their worst-case EVE loss under the SOT scenarios. The ECB reviews IRRBB as a core component of the SREP — a large or growing IRRBB position typically results in a higher P2R or P2G. | IRB Explainer — Pillar 2 |