Understanding SDLT Calculations for Index-Linked Rent and RPI Adjustments

SDLT treatment of RPI-linked rent reviews

For SDLT on leases, future rent changes are usually ignored if they are caused only by changes in the retail prices index (RPI). HMRC says this also applies to capped, floored and increase-only RPI clauses, but not to clauses using “RPI plus”, “RPI minus” or a different index, so the exact lease wording is important.

• SDLT on lease rent is based on the net present value of rent payable over the term, so it matters whether future rent is treated as fixed or variable.
• If a rent review is purely linked to RPI, the adjustment is generally ignored and the rent is not treated as variable for this SDLT purpose.
• HMRC accepts that pure RPI clauses can still qualify even if they include a cap, a floor, or an increase-only provision.
• Using an earlier RPI figure, such as one from up to three months before the review date, can still count as being in line with RPI.
• The exclusion does not usually apply if the clause uses “RPI plus”, “RPI minus”, another index such as RPIX, or any formula adding something beyond RPI itself.
• Small drafting differences can change the SDLT result, and unusual clauses or replacement index provisions may need closer legal review.

Scroll down for the full analysis.

SDLT and index-linked rent: when RPI rent reviews are ignored

This page explains how Stamp Duty Land Tax applies where rent under a lease changes by reference to inflation. The key point is that some RPI-linked rent changes are ignored when working out SDLT on rent, but only if the change is solely due to adjustments in line with the retail prices index. Small drafting differences can change the result.

What this rule is about

SDLT on leases can depend on the net present value of the rent payable over the term. That requires you to work out what rent is to be treated as payable. This becomes more complicated where the lease rent can go up or down in future because of a formula.

The rule covered here deals with one particular type of future rent change: index linking. The legislation treats certain RPI-only adjustments as excluded adjustments. If an adjustment is excluded, the rent is not treated as variable for this purpose.

This matters because if the rent is treated as variable or uncertain, that can affect how the rent is calculated for SDLT. By contrast, if the adjustment is ignored under the RPI rule, the SDLT calculation proceeds without treating those future RPI movements as variable rent.

What the official source says

HMRC’s view is that rent changes are ignored where the whole change in rent is solely due to adjustments in line with the retail prices index, or RPI. In those cases, the rent is not treated as variable.

This also covers capped RPI adjustments where the lease sets a minimum or maximum limit on the RPI movement. HMRC says those adjustments are still within the exclusion.

But HMRC also says the exclusion does not extend to:

• adjustments on an “RPI plus” or “RPI minus” basis, such as RPI plus 1%
• adjustments by reference to another index, such as RPIX

The reason given is that the legislation refers specifically to the retail prices index. If the formula adds or subtracts something from RPI, or uses a different index, the adjustment is not wholly “in line with” RPI.

HMRC further accepts that an adjustment can still count as being in line with RPI even if it uses an RPI figure from up to three months before the review date. For example, a June rent review based on the previous March’s RPI is accepted.

HMRC also accepts that an increase-only RPI clause can still be ignored. So if the lease says the rent goes up only if RPI is positive, that still counts as an adjustment in line with RPI.

What this means in practice

If a lease rent review clause is a pure RPI mechanism, SDLT does not treat the rent as variable just because inflation may change the amount payable in future.

In practice, this means you need to look closely at the drafting of the rent review clause, not just its commercial label. Two clauses may both be described as inflation-linked, but one may be ignored for SDLT and the other may not.

A straightforward RPI review, even with a floor or cap, will usually fall within the exclusion described by HMRC. But once the formula moves away from pure RPI, the position changes. A clause using RPI plus 2%, or substituting a different index, is not treated in the same way.

That distinction can affect the SDLT rent calculation and therefore the tax due on the lease.

How to analyse it

When reviewing a lease, ask these questions in order:

• Does the rent change under a formula linked to the retail prices index?
• Is the whole change in rent solely due to that RPI adjustment?
• Does the clause simply cap or floor the RPI movement, rather than adding a separate uplift or reduction?
• Is the clause “increase-only” so that rent rises with positive RPI but does not fall if RPI is negative? HMRC says that can still be ignored.
• Does the clause use RPI from a short earlier period, such as up to three months before the review date? HMRC accepts that this can still be treated as in line with RPI.
• Does the clause instead use “RPI plus”, “RPI minus”, or another index altogether? If so, HMRC says the exclusion does not apply.

The central question is whether the rent movement is wholly attributable to RPI itself. If something else is built into the formula, the adjustment is no longer purely in line with RPI.

Example

Illustration: a 10-year lease provides that the yearly rent is reviewed every five years in line with RPI, subject to a maximum increase of 4% and no reduction if RPI is negative. On HMRC’s approach, those review changes are still ignored for this SDLT point, because they are treated as being in line with RPI even though the clause is capped and increase-only.

By contrast, if the lease says the rent rises by RPI plus 1% at each review, that extra 1% means the adjustment is not wholly in line with RPI. HMRC says that type of clause must be taken into account when calculating the net present value.

Why this can be difficult in practice

The difficulty is often in the drafting detail. A clause may look like a normal inflation review, but a small addition can take it outside the exclusion. “RPI plus”, “RPI minus”, substitution of another index, or a hybrid formula can all matter.

Another practical issue is that this guidance reflects HMRC’s interpretation of the legislation. The legislation itself is the starting point, and the exact wording of the lease remains critical.

There can also be edge cases where the clause is mostly RPI-based but contains fallback provisions, replacement indices, or formula changes if RPI is discontinued. The source material here does not resolve every such situation, so those cases may need closer analysis.

Key takeaways

• Pure RPI-linked rent adjustments are generally ignored for SDLT rent calculations, so the rent is not treated as variable for this reason alone.
• Capped, floored, and increase-only RPI clauses can still fall within that treatment according to HMRC.
• “RPI plus”, “RPI minus”, or use of a different index are not treated as pure RPI adjustments and may affect the SDLT calculation.

This page was last updated on 24 March 2026

Useful article? You may find it helpful to read the original guidance here: Understanding SDLT Calculations for Index-Linked Rent and RPI Adjustments

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