Japanese knotweed doesn’t have to stop a house sale. What can stop it — or land you with a lawsuit long after completion — is getting the paperwork wrong. If you’re selling a property in England or Wales, that paperwork centres on one document: the Law Society’s TA6 Property Information Form. Here’s exactly what it asks, why sellers get caught out, and what to do if you’ve got knotweed on your land.
What the TA6 Form Actually Is
The TA6 is the standard “Seller’s Property Information Form” used in the vast majority of residential property sales in England and Wales. Your solicitor gives it to you to complete, and your answers are passed directly to the buyer’s solicitor as part of the conveyancing process. Since March 2026, conveyancers accredited under the Law Society’s Conveyancing Quality Scheme have been required to use the form’s sixth edition — a shorter, plainer version than its predecessor, but one that still asks the Japanese knotweed question in full, sitting within the form’s environmental matters section.
The question is simple to read and easy to get wrong: is the property affected by Japanese knotweed? You have three options — Yes, No, or Not known — and each one carries real legal weight.
Yes, No, or Not Known: Why the Wording Matters
“Yes” means you’re declaring that knotweed is present — whether visible above ground or as rhizome (root) beneath it — either on the property itself or within three metres of the boundary. This isn’t automatically a deal-breaker. Buyers and lenders increasingly expect to see knotweed disclosed and professionally managed rather than magically absent.
“No” is the answer that causes the most trouble. According to the Law Society’s own guidance notes, you can only answer “No” if you are certain — not “fairly sure,” not “haven’t seen any” — that no knotweed rhizome exists anywhere on the property or within three metres of its boundary, even if nothing is visible above ground. Given that knotweed can lie dormant and undetectable for years before resurfacing, that’s a high bar for most sellers to clear honestly without a professional survey behind them.
“Not known” is the honest middle ground for sellers who genuinely haven’t checked or aren’t sure, and it’s the answer solicitors most often recommend when a seller has any doubt at all. It shifts the responsibility for further investigation onto the buyer, rather than leaving the seller exposed.
What Happens If You Get It Wrong
Answering “No” when knotweed is later discovered on the property isn’t just embarrassing — it can amount to misrepresentation, and the financial consequences can dwarf the cost of treatment. In one widely reported case, a buyer who purchased a London property for £700,000 successfully sued the seller after discovering knotweed the seller had denied on the TA6 form, with the resulting damages and legal costs running into six figures. The lesson conveyancing solicitors draw from cases like this is consistent: the risk isn’t having knotweed. The risk is what you say about it on the form.
How Knotweed Now Affects Mortgages: The RICS Categories
It used to be much simpler to scare people about knotweed than to actually assess it. Until 2022, surveyors used a blunt “seven-metre rule” — if knotweed was growing anywhere within seven metres of a property, it was treated as a serious risk, regardless of whether it was actually causing any damage. The Royal Institution of Chartered Surveyors (RICS) scrapped that approach in March 2022 in favour of a more proportionate, evidence-based system built around four Management Categories:
- Category A — Action: Knotweed is visibly damaging a structure. Lenders will typically apply a mortgage retention until a specialist remediation plan is in place.
- Category B — Action: Knotweed is present on-site, isn’t damaging a structure, but is likely to restrict use of a garden or amenity space. A retention and specialist management plan are again the usual outcome.
- Category C — Manage: Knotweed is present but isn’t causing damage or restricting use. Mortgages generally proceed without a retention, though buyers and lenders often still expect evidence of an ongoing management plan.
- Category D — Report: Knotweed is visible on neighbouring land within three metres of the boundary, but not on the property itself. No retention is usually required, though a specialist may be asked to advise on the risk of future encroachment.
This shift means knotweed alone is far less likely to sink a sale outright than it was a decade ago — but categories A and B still typically require a PCA-accredited contractor’s management plan, backed by an insurance-backed guarantee, before most lenders will release funds.
What Sellers Should Actually Do
If you know or suspect knotweed is present, the worst option is guessing on the TA6 form and hoping nobody looks too closely. The best option is to get ahead of it before you list the property:
- Commission a specialist survey before you list. A clear, dated report from an accredited surveyor gives you the evidence to answer the TA6 question accurately — whichever answer that turns out to be — and hands your solicitor something concrete to work with.
- If knotweed is confirmed, get a professional management plan in place early. Buyers and lenders respond far better to an active, documented treatment plan than to a bare admission with no evidence anything is being done about it.
- Use a PCA accredited contractor. Most mortgage lenders specifically require treatment to be carried out — or at least verified — by an accredited specialist before they’ll lend against a Category A or B property.
- Get an insurance-backed guarantee. This is often the single document that turns a stalled sale into a completed one, since it gives the buyer’s lender confidence the problem won’t resurface after completion.
- Keep every record. Survey reports, treatment invoices, guarantees and correspondence all help demonstrate exactly what you knew and when — the strongest possible protection if a dispute ever arises after completion.
How Eco Control Solutions Can Help You Sell With Confidence
We work with sellers, estate agents and solicitors across the whole of the UK to take the guesswork out of the TA6 knotweed question. Our service includes:
- Pre-sale knotweed surveys, giving you clear, documented evidence to complete the TA6 form accurately and with confidence.
- PCA-accredited treatment plans tailored to your property’s RICS Management Category, whether that’s urgent action or straightforward ongoing management.
- Insurance-backed guarantees, accepted by the vast majority of UK mortgage lenders, to reassure buyers and keep your sale on track.
- Clear documentation for your solicitor, so your survey reports and treatment records are ready to hand over the moment a buyer’s solicitor asks for them.
Knotweed doesn’t have to derail a sale — but guessing on the TA6 form is how sellers end up in court. Get a professional survey in place first, and the rest of the process becomes far more straightforward.
Get in touch today for a free, no-obligation knotweed survey — wherever you’re based in the UK.
