How DB Pensions Increase in Payment: RPI, CPI, and the LPI Cap Explained

The annual increase applied to a defined benefit pension in payment is not a trivial matter. Over a 20- or 25-year retirement, the difference between a pension that increases by 2.5% per year and one that increases by 3.5% per year compounds to a very large number. For a pension of £30,000/year, a 1% additional annual increase over 25 years produces cumulative additional income of approximately £90,000–£100,000 in nominal terms.

Understanding the rules governing how your pension increases — and whether your scheme is doing the right thing by you — is an aspect of pension administration that too few retirees interrogate.

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The Legal Minimum: Statutory Pension Increases

The Pensions Act 1995 and subsequent legislation require registered DB pension schemes to apply Limited Price Indexation (LPI) to benefits in payment. The minimum increase required by law depends on when the pension benefits accrued:

Pre-6 April 1997 accrual (GMP and pre-'97 benefits)

Benefits accrued before April 1997 are subject to different rules:

• Guaranteed Minimum Pension (GMP): the contracted-out portion accrued before April 1997 is revalued by the State for the GMP element. Specifically, post-1988 GMP is increased by the scheme in line with CPI up to 3% per year; the State (DWP, via the State Pension) makes up any shortfall above 3% on the GMP portion. Pre-1988 GMP attracts no statutory in-payment increases from the scheme — the State handles all indexation.
• Non-GMP pre-1997 benefits: no statutory requirement for schemes to increase these. Many schemes choose to do so, but it is not legally required.

6 April 1997 to 5 April 2005 accrual

Benefits accrued in this window are subject to LPI with a 5% annual cap (formerly based on RPI). The increase each year is:

Pension increase = min(RPI increase, 5%)

So if RPI is 3.2%, the pension increases by 3.2%. If RPI is 6.8%, the pension increases by only 5%.

Post-6 April 2005 accrual

For benefits accrued from April 2005 onwards, the LPI cap was reduced to 2.5%. The increase is:

Pension increase = min(CPI increase, 2.5%)

Note: the Pensions Act 2011 changed the statutory measure from RPI to CPI for most private sector schemes from April 2011. However, the change applies only where the scheme rules refer to the "statutory minimum" or a similar formulation — schemes with rules that specify RPI explicitly may continue to use RPI even for post-2011 accrual.

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CPI vs RPI: Why It Matters

The shift from RPI to CPI as the statutory measure was controversial because RPI is typically higher than CPI:

• RPI includes mortgage interest costs and certain other housing costs excluded from CPI
• RPI uses an arithmetic mean; CPI uses a geometric mean — this "formula effect" alone accounts for approximately 0.5–1% of the typical difference
• Over the period 2000–2025, RPI averaged approximately 0.7–1.0% higher than CPI annually

For a pensioner, receiving increases linked to CPI rather than RPI means gradually falling behind the cost of living if their actual spending pattern reflects the RPI basket more closely. Pensioners who own their homes outright (no mortgage) may find CPI more representative of their actual expenditure, since mortgage interest is excluded from both CPI and their own spending. Pensioners who rent may find CPI underestimates their real cost increases.

RPI's future: in 2020 the UK Statistics Authority and the Treasury confirmed a reform of RPI methodology, aligning it with CPIH (CPI including owner occupiers' housing costs), to take effect from February 2030. As of 2026, RPI and CPI remain different measures, and the reform is not yet in force. Some legacy DB schemes that specify RPI by scheme rules continue to use it; scheme advisers and actuaries debate the legal position on reform.

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What "LPI" Means in Practice

Limited Price Indexation means that the pension increases each year by the lower of:

1. The applicable inflation measure (CPI or RPI), and
2. The specified cap (5% for pre-2005 accrual; 2.5% for post-2005 accrual)

The pension will never decrease even if inflation is negative. The floor is 0%.

Example (mixed-accrual pension):

A 65-year-old retired in 2025 from a corporate DB scheme with benefits accrued over two periods:

• Pre-April 2005 accrual: pension of £15,000/year (LPI cap 5%)
• Post-April 2005 accrual: pension of £10,000/year (LPI cap 2.5%)

CPI for 2025/26 announced in October 2025: 3.8%

Increases for 2026:

• Pre-2005 portion: increases by 3.8% (CPI < 5% cap) = £15,570
• Post-2005 portion: increases by 2.5% (CPI 3.8% > 2.5% cap) = £10,250

Total pension in 2026: £25,820 (was £25,000)

In a year when CPI is 7%:

• Pre-2005 portion: increases by 5% (cap applies) = £15,750
• Post-2005 portion: increases by 2.5% (cap applies) = £10,250

The difference between receiving the full CPI increase (7%) and the capped increase illustrates the cost to the member of the cap in a high-inflation environment.

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Schemes That Exceed the Statutory Minimum

Many DB schemes — particularly in the public sector and some legacy corporate schemes — provide increases above the statutory minimum. Common examples:

• Public sector schemes (NHS 1995/2008 Section, teachers, civil service, LGPS): increase at CPI (no cap), meaning the full CPI uplift is paid each year regardless of how high inflation rises. In 2022/23, pensions increased by up to 10.1% (September 2022 CPI).
• Some legacy corporate schemes: may have rules providing RPI-linked increases with no cap — these are increasingly rare but still exist in some former nationalised industry schemes.
• Escalating annuities: some members who converted DB to an annuity at retirement chose a "3% escalating" or "5% escalating" annuity, providing fixed annual increases. These are guaranteed by the annuity insurer but are not inflation-linked.

For public sector members — NHS, teachers, local government, armed forces — the absence of an LPI cap means high-inflation years are fully captured, making public sector pensions significantly more valuable in real terms during inflationary periods.

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Checking Your Scheme Rules

To know exactly what increases you are entitled to, you need to consult your scheme's Trust Deed and Rules (for a private sector scheme) or the relevant statutory instrument and scheme regulations (for a public sector scheme). The scheme's annual report and benefit statement should also summarise the increase basis.

Key questions to ask your scheme administrator:

1. Which measure is used (CPI or RPI)?
2. Is there a cap, and if so, at what rate?
3. Does the cap apply to all my benefits or only post-2005 accrual?
4. What is the date in the year on which my pension is reviewed?
5. Is the reference inflation figure September of the prior year, or some other month?

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The Reference Month: September CPI

Most DB pension increases — and the annual uprating of State Pension — are based on the September CPI figure published by the ONS in mid-October each year. The increase is typically applied the following April (for state pension and many public sector schemes) or at the scheme's anniversary date.

This timing means the inflation rate "locked in" to your pension for a given year was measured 6–12 months prior. In rapidly changing inflationary environments, this lag can result in increases that are either higher or lower than current inflation at the time the increase is applied.

Some schemes use a different reference month (December, January) — again, check your scheme's specific rules.

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Pension Increase Exchange (PIE): Trading Future Increases for a Higher Current Pension

Some DB schemes offer a Pension Increase Exchange (PIE): a one-time option to give up some or all future statutory indexation increases in exchange for a higher immediate pension. For example:

• Current pension: £20,000/year with CPI LPI (2.5% cap)
• PIE offer: £24,000/year with no future increases (flat pension)

The member must decide whether the higher immediate income outweighs the loss of future inflationary protection. This is an actuarial calculation that depends on the member's age, health, expected longevity, current inflation level, and personal circumstances. A PIE can be attractive for:

• Members with reduced life expectancy
• Members who have other inflation-proofed income (State Pension, index-linked annuity)
• Members who prefer the certainty of known income

A PIE can be unattractive for:

• Members in good health with long expected retirements
• Members in periods of high inflation (where the future increases given up are valuable)
• Members without other inflation-protected income

A PIE is irreversible — once accepted, you cannot undo it. Specialist financial advice from a regulated IFA is essential before accepting a PIE offer.

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Divorce and Pension Increases

Where a pension sharing order has transferred part of a DB pension to a former spouse, the transferred amount becomes a "pension credit" held in the scheme for the receiving spouse. The pension credit's in-payment increases depend on the scheme rules and may or may not be the same as the member's own pension. Some schemes apply statutory minimum increases to the pension credit; others may have different rules. Check with the scheme administrator if this affects you.

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Interaction with the Annual Allowance

Pension increases in payment for a DB scheme are reflected in the pension input amount calculation for the annual allowance. The CPI uplift applied to the opening pension is part of the statutory formula — specifically, the opening pension is multiplied by the CPI factor before the closing pension is compared against it. This means that high inflation years can paradoxically reduce the pension input amount (because the opening pension is uplifted more, and the closing pension needs to grow by more than the CPI-uplifted opening pension before it contributes to a positive input amount).

For members who are still accruing in a DB scheme and are concerned about the annual allowance, understanding the CPI revaluation in the PIA formula is important. See the separate Global Investments guide on annual allowance charge calculation.

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Compliance Caveats

Pension increase rules are set by legislation, trust deed, and scheme regulations — all of which may change. The statutory minimum basis changed from RPI to CPI for private sector schemes in 2011 and may be subject to further reform. Public sector scheme rules are set by statutory instrument and have their own reform processes. The information in this guide reflects the position as of 2026 and does not constitute regulated financial advice. For information specific to your scheme's increase provisions, contact your scheme administrator directly. For advice on whether a Pension Increase Exchange is appropriate for your circumstances, seek regulated financial advice from an FCA-authorised adviser.

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How Global Investments Can Help

DB pension increases are a significant element of retirement income planning — particularly for clients who retired in periods of low inflation and are now experiencing the compound effect of higher CPI on their in-payment pension. Global Investments can help you understand your scheme's increase basis, model how your pension income will evolve over time, and integrate this into a broader retirement income strategy that accounts for all your income sources. Contact our team to start the conversation.