Variable rent in a lease: working out SDLT on uncertain rent
Variable lease rent and SDLT
Where lease rent is not fixed, SDLT may still be due from the start. The method depends on why the amount is unknown.
- Assume contingent rent will be paid.
- Make a reasonable estimate for uncertain rent.
- Keep evidence supporting that estimate.
Scroll down for the full analysis.
Read the original guidance here:
Variable rent in a lease: working out SDLT on uncertain rent
Variable rent in a lease: working out SDLT on uncertain rent
If your lease rent may change or depend on a future event, you cannot simply leave it out of the stamp duty calculation. For the first five years, when the amount cannot yet be known or payment depends on a future condition, you will usually make a reasonable estimate or assume payment. That can affect the SDLT due when the lease starts.
What this rule is about
SDLT on lease rent is worked out by reference to its net present value, often called NPV, which brings rent payable over the lease into a single tax calculation. It puts the rent due across the whole lease into one figure for tax purposes.
That is simple where every payment is fixed. It is harder where the lease says the rent will follow future market rents, business results or an event that may never happen.
The law separates two common problems. The difference matters.
What the official source says
HMRC’s manual says that special rules apply where lease rent varies, is contingent, uncertain or cannot yet be worked out. The legislation sets the method; HMRC’s manual explains its view of how it applies.
- Contingent rent depends on an uncertain future event.
- For example, extra rent may be due only if planning permission is granted.
- For contingent rent in the first five years, assume the amount will be paid.
- Uncertain rent has an amount that depends on future events.
- Market-rent reviews and rent linked to business results can fall into this group.
- For uncertain rent in the first five years, use a reasonable estimate.
- For every year after year five, where rent was uncertain or contingent during the opening five years, use the highest rent arising in any consecutive twelve-month period within those five years.
- Ignore an adjustment to rent where it follows only the retail prices index.
HMRC says an estimate does not always need a professional valuation. Still, you should keep clear records showing how you reached it. A guess with no working behind it is unlikely to help if HMRC asks questions later.
What this means in practice
Begin with the lease wording rather than the rent figure on the first invoice. A low starting rent may not be the figure that drives the SDLT calculation if the lease includes a review or a conditional increase.
You may need to put a value on something that has not happened yet. The law requires that at the start. It does not wait until the future becomes clear.
- Read every rent review and turnover-rent clause.
- Identify payments due only if a named event happens.
- Separate those payments from rent with an unknown future level.
- Prepare a sensible estimate for the first five years where needed.
- Keep the forecasts, comparables or other material used.
- Find the highest rolling twelve-month rent in those first five years.
- Use that amount for the later years of the NPV calculation.
This is the part people often miss: the general SDLT rules for later changes to uncertain amounts do not apply to rent. Nor can you defer SDLT payment just because lease rent is contingent or uncertain.
That does not mean the first calculation can never change. Schedule 17A has a separate route for adjusting the position in certain cases when rent in the first five years becomes known, or when year five ends.
How to analyse it
Ask one question at a time. A label in the lease, such as “review rent”, does not settle the point.
- What rent is fixed when the lease starts?
- Which clause makes the amount change?
- Does payment depend on a future event happening or not happening?
- Or does the amount depend on a future fact, such as market rent or turnover?
- Does the clause adjust rent solely by the retail prices index?
- What is a reasonable estimate for each affected part of the first five years?
- Which consecutive twelve-month period produces the highest first-five-year rent?
- Has an event later made the first-five-year rent known?
Write down the answer to each question. That creates an audit trail and makes the calculation easier to check.
Example
Amir takes a ten-year shop lease. Rent is £20,000 in year one. For years two to five, it will be the market rent at each review date. Based on local evidence, Amir estimates £23,000 a year for each of those four years.
For the SDLT rent calculation, the first five years use £20,000 and the reasonable estimates of £23,000. The highest consecutive twelve-month amount in that period is £23,000. The later years are therefore calculated using £23,000 a year.
Now change one fact. If the lease says an extra £5,000 is due only if planning permission is granted, that extra amount is contingent rent. For the first five years, the calculation assumes it will be paid.
Why this can be difficult in practice
Lease clauses can combine several moving parts. A rent review may depend on market evidence, a tenant’s sales, a planning decision and an index adjustment. Each part may need separate treatment.
- Calling rent “variable” does not explain why it varies.
- A turnover clause may need financial forecasts and careful reading.
- Market evidence available when the lease starts can be important.
- A later lower rent does not automatically undo the original calculation.
- The special adjustment process is not the same as the general rules in sections 80 and 90.
- RPI-only adjustments are treated differently from wider index or review clauses.
If you only remember one thing, make it this: retain the basis for any estimate made at the start of the lease. The final rent may be unknown, but the reasoning behind your figure should not be.
Key takeaways
- Unknown lease rent still goes into the SDLT calculation.
- Estimate uncertain rent, but assume contingent rent will be paid.
- Keep evidence showing how you reached the estimate.
Technical analysis
For advisers, and for anyone who wants to check the law behind this page. You do not need this section to understand the guidance above.
Legislation
- FA 2003 Schedule 5 para 2 — tax on rent uses its net present value
- FA 2003 section 51 — treatment of contingent and uncertain consideration
- FA 2003 Schedule 17A para 7 — working out SDLT rent where amounts vary
- FA 2003 Schedule 17A para 8 — later adjustment when uncertain rent becomes known
- FA 2003 section 80 — general adjustment when consideration becomes known
- FA 2003 section 90 — deferring tax on contingent or uncertain consideration
Official guidance
The pages below are HMRC’s guidance. Guidance is not law. It sets out how HMRC reads the legislation, and it is not binding on you, on a tribunal or on a court. Where guidance and the legislation differ, the legislation wins. HMRC can also change or withdraw guidance, and it may not cover your facts.
Where this is not settled
- What is a reasonable estimate depends on the lease terms and the evidence available when the lease starts.
- A clause may be difficult to classify where it contains both a future condition and an estimate-based rent review.
- The supplied legislation is current only to 17 November 2025. A lease with an effective date after that date needs a current-law check.
Evidence you would need
This kind of case is decided on the facts of the individual property. These are the records that usually settle it, and the ones an adviser would ask you for.
- The signed lease and every rent review clause
- A schedule of rent expected in each of the first five years
- Evidence supporting any estimate, such as forecasts or comparable rents
- Details of any planning condition, turnover target or other future event
- Records showing whether an RPI-only adjustment applies
Explore this with an AI
Readers often want to test their own situation. Copy the prompt below into ChatGPT, Claude or Gemini. It hands the model the actual legislation for this page rather than letting it answer from memory, and tells it to be explicit about what is uncertain. What comes back is information, not advice – check it against the links above.
I am researching UK Stamp Duty Land Tax (SDLT), which applies in England and Northern Ireland. MY QUESTION Variable rent in a lease: working out SDLT on uncertain rent [Replace this with your own situation: what you are buying, the price, the dates, who the buyer is, and what you plan to do with the property.] THE LAW THIS TURNS ON - FA 2003 Schedule 5 para 2 - tax on rent uses its net present value https://www.legislation.gov.uk/ukpga/2003/14/schedule/5/paragraph/2/2025-11-17 - FA 2003 section 51 - treatment of contingent and uncertain consideration https://www.legislation.gov.uk/ukpga/2003/14/section/51/2025-11-17 - FA 2003 Schedule 17A para 7 - working out SDLT rent where amounts vary https://www.legislation.gov.uk/ukpga/2003/14/schedule/17A/paragraph/7/2025-11-17 - FA 2003 Schedule 17A para 8 - later adjustment when uncertain rent becomes known https://www.legislation.gov.uk/ukpga/2003/14/schedule/17A/paragraph/8/2025-11-17 - FA 2003 section 80 - general adjustment when consideration becomes known https://www.legislation.gov.uk/ukpga/2003/14/section/80/2025-11-17 - FA 2003 section 90 - deferring tax on contingent or uncertain consideration https://www.legislation.gov.uk/ukpga/2003/14/section/90/2025-11-17 Guidance page from HMRC on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm13150 HOW I WANT YOU TO ANSWER 1. Work from the legislation above. Read it before answering. Guidance from HMRC is its view of the law, not the law, and does not bind a tribunal or a court. 2. Tell me what the rule actually requires, in plain English. 3. Tell me which facts decide the answer, and which facts would change it. 4. Tell me what evidence I would need to support the position. 5. Be explicit about anything unsettled or fact-sensitive. Do not guess. 6. Your training data has a cutoff and SDLT rates and reliefs change at fiscal events. Say so if you are not sure the law is current. POINTS ALREADY KNOWN TO BE UNCERTAIN ON THIS TOPIC - What is a reasonable estimate depends on the lease terms and the evidence available when the lease starts. - A clause may be difficult to classify where it contains both a future condition and an estimate-based rent review. - The supplied legislation is current only to 17 November 2025. A lease with an effective date after that date needs a current-law check. Do not give me a conclusion you cannot support from the provisions above.
Legislation links show Finance Act 2003 as it stood on 2025-11-17. The law may have changed since, and the rules that apply are those in force on the date of your transaction. The official guidance this page is based on is here.
This page was last updated on 31 August 2026
Useful article? You may find it helpful to read the original guidance here: Variable rent in a lease: working out SDLT on uncertain rent
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