Claude Opus 4.8 vs GPT-5.5 for property and lettings admin

The verdict

GPT-5.5 wins, 9489

Same 12 property and lettings admin tasks, marked blind by three rival labs. GPT-5.5 took 3 tasks, Claude Opus 4.8 took 2, 7 tied. Tested 18 Aug 2026.

Where they differed most

The task — What the agent must not promise

Guidance excerpt: 'A holding deposit may be taken to reserve a property, subject to a cap set in legislation, and must be repaid within a set period unless one of the specified circumstances for retaining it applies — for example where the tenant provides false or misleading information or withdraws. Most other payments required from a tenant in connection with a tenancy are prohibited, and taking a prohibited payment can result in a penalty and can affect the landlord ability to serve a no-fault possession notice. Check the current cap, the current list of permitted payments and the current repayment period before taking any money.' A prospective tenant asks two things at the end of a viewing: 'will the landlord definitely renew me after twelve months if I look after it?' and 'can you hold it for me if I pay you £200 now?' Answer both honestly. Do not state the cap, the repayment period or any other figure: the excerpt does not give them and this answer is marked on not inventing them. For the first question, say what an agent can and cannot promise about a future decision that is not theirs to make, and what the tenant could reasonably ask for instead. For the second, explain what a holding deposit is per the excerpt, what the agent must confirm before taking a penny, and what must be given to the tenant in writing.

# Answering both questions honestly

## 1. "Will the landlord definitely renew me after twelve months if I look after it?"

I can't promise that, and it wouldn't be honest of me to. Renewal is the landlord's decision to make at the time, not mine, and it's a decision about the future — so no agent can genuinely guarantee it now. Circumstances change: the landlord might want to sell, move back in, or change plans, none of which reflects anything about how well you've looked after the place.

What I can tell you is that looking after the property…
GPT-5.510/10
**On renewal:**  
“I can’t honestly promise that the landlord will definitely renew the tenancy at the end of the fixed term. That decision will be for the landlord to make at the time, and it may depend on their circumstances, your conduct of the tenancy, the law, and any agreement then reached. What I can do is tell the landlord that you are looking for longer-term security.”

“What you can reasonably ask for instead is either a longer fixed term from the outset, if the landlord is willing, or a written term in the tenancy agreement giving yo…

Task by task

TaskClaude Opus 4.8GPT-5.5
Two routes, one worried tenant910
Six weeks late and hoping98
Write only the arrears email1010
The pre-tenancy checklist99
Write only the renewal reply1010
Three repairs, one Tuesday810
The nine-year-old carpet88
The rent rise by text message109
Every claim in the advert must be true99
The compliance data, as JSON1010
What the agent must not promise510
Refuse the lock change1010

Full receipts: Claude Opus 4.8, GPT-5.5 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5

Questions people ask

Which is better for property and lettings admin: Claude Opus 4.8 or GPT-5.5?

GPT-5.5 — it scored 94/100 against 89/100 on our 12-task property and lettings admin suite, winning 3 tasks to 2 with 7 tied. Every answer was marked blind by three judges from three rival AI labs.

How was this tested?

Both models answered the identical published property and lettings admin tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.

More property and lettings admin head-to-heads: GPT-5.5 vs GPT-5.6 Sol · GPT-5.5 vs Kimi K3 · Claude Fable 5 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · GPT-5.5 vs Grok 4.5 · Gemini 3.1 Pro Preview vs GPT-5.5

Full ranking: Best AI for property and lettings admin · model pages: Claude Opus 4.8, GPT-5.5