You can sell a house with Japanese knotweed, but in England and Wales you must declare it honestly on the TA6 Property Information Form, even if it has already been treated. A specialist survey and, where needed, a management plan with an insurance-backed guarantee give buyers and their lenders the evidence they will look for, so it pays to have them in place before you list.
The TA6 form
Having knotweed on your land is not illegal, but you must be open about it when you sell. Most standard residential sales in England and Wales use the Law Society's TA6 Property Information Form. The 6th edition (2025) replaced the 4th and 5th editions, which the licensed suppliers have withdrawn, and firms in the Conveyancing Quality Scheme (CQS) must use it for new transactions where the solicitor was instructed on or after 30 March 2026.
Knotweed is covered by question 8.6, on whether it is present, and 8.7, on any survey and management. The forms are Law Society copyright and not available to the public, but your conveyancer can take you through them.
The Law Society's explanatory notes treat a property as usually at risk if knotweed grows on it or within three metres of its boundary, so knotweed on a neighbour's land close to yours can be relevant. Rhizome, the underground stem, can be present with nothing visible above ground, which is why many sellers answer "not known". You should attach any survey report or management plan you hold, say if you do not know an answer, and tell your solicitor if any answer becomes wrong or changes. Buyers can rely on what you say, and if your information is misleading, the buyer may be able to claim compensation after completion.
Answer the TA6 accurately
If you have seen knotweed, had it treated or hold a survey or plan, say so and attach the paperwork. If you genuinely do not know, say that instead.Declaring past treatment
RICS states that a seller will still have to declare knotweed on the TA6 after remediation. It accepts that some stigma may affect resale value, but expects the effect to be much smaller than at purchase and to reduce over time.
In 2019 the House of Commons Science and Technology Committee asked the Law Society to review the knotweed question, including whether the need to declare past knotweed should end after successful excavation with no regrowth. The explanatory notes for the 6th edition mention no such expiry, so if knotweed was dealt with years ago and you are unsure how to answer, ask your conveyancer.
A completion certificate and a guarantee you can pass to the buyer show that the problem was handled properly, which is the evidence buyers and their lenders look for.
The buyer's survey
Surveyors and mortgage valuers who are RICS members must comply with the RICS professional standard Japanese knotweed and residential property, in force since 23 March 2022. They can take account only of what is visible on the day, and place any knotweed they see in one of four Management Categories.
| Category | When it applies | Likely effect on value (RICS) |
|---|---|---|
| A: Action | Knotweed on the property is causing visible material damage to a structure, such as a garage, outbuilding, conservatory, path, or retaining or boundary wall | Likely to be affected |
| B: Action | It is not causing that damage, but is likely to prevent use of, or restrict access to, amenity space such as lawns, patios, paths and driveways | May be affected |
| C: Manage | It is on the property but neither damaging significant structures nor restricting amenity space | Usually modest |
| D: Report | It is not seen on the property but is visible on adjoining land within 3 m of the boundary | Usually limited |
Knotweed along a boundary, in boundary hedging or affecting boundary walls counts as on the property. Knotweed seen more than 3 m beyond the boundary is normally just recorded in the valuer's notes.
Where the surveyor knows of knotweed they cannot see, for example from your TA6 answers or the solicitor's enquiries, the standard says they should look at what evidence exists. If there is a recognised remediation strategy, they should recommend that the buyer or their legal adviser obtains and inspects the documents. Without satisfactory evidence of a properly planned programme, they should recommend further investigation by a recognised contractor. Having your paperwork ready keeps the sale moving.
Check your likely RICS categoryLender requirements
For Categories A and B, RICS anticipates that most lenders will require three things as a condition of the mortgage, subject to a retention from the advance: an inspection by a specialist from a recognised trade body, completion of the recommended works under a Japanese Knotweed Management Plan (JKMP), and an insurance-backed guarantee. As of 2022 it named the Property Care Association (PCA) and the Invasive Non-Native Specialists Association (INNSA) as the two associations providing this assurance. For Categories C and D, no retention should normally be imposed.
These are expectations, not lender commitments. Each lender sets its own mortgage policy on knotweed, some do not make retentions at all, and when a valuer acts for a lender, the lender's instructions take precedence over the RICS guidance.
Management plans
Under the RICS standard, a JKMP should include:
- a description and accurate record of the infestation, with a scaled plan showing dimensions
- the contractor's details and the methods to be used
- a treatment schedule, updated as treatments are carried out
- a completion certificate once the plan is finished, including a two-year "no growth" period
- a guarantee of at least five years after completion, with third-party insurance so it survives if the contractor goes out of business (an insurance-backed guarantee)
RICS also notes that lenders take reassurance when the current owner has paid the costs up front, and when the plan is transferable to later owners and covers the whole property. Herbicide control needs at least four years of treatment and monitoring before a completion certificate, so you may sell part-way through a plan, which makes transferability all the more important. Management plans and their guarantees are issued by independent specialists.
Arrange a specialist survey
We can introduce you to up to three Property Care Association members who cover your area. There is no charge for the introduction.
Find a specialistEffect on value
There is no standard discount. RICS tells valuers not to apply a standard percentage reduction for knotweed, nor to reflect only the cost of remediation, but to weigh five factors: the impact on the market before remediation, restrictions on use, the impact during remediation, any infestation on adjoining land, and the impact on saleability after remediation. Some properties keep a stigma for a period even after effective remediation.
On structural risk, RICS says knotweed rarely causes structural damage to substantial buildings such as houses, although it can damage lightweight structures, walls, paths, hardstandings and drains.
Preparing to sell
Start by confirming what you have. The photo check gives an indicative view, while a specialist survey produces a report you can attach to the TA6. Check what is growing on your neighbours' side of the boundary too.
If treatment is needed, starting it before you list lets you show buyers a plan and schedule already under way. Keep the survey report, JKMP, treatment records, any completion certificate and the guarantee together, and check that the guarantee is insurance-backed and can pass to the buyer. Confirm any specialist's membership on the PCA member search, or with INNSA, then brief your conveyancer.
If you need a survey or management plan, we can introduce you to up to three independent specialists who cover your area.