DeepSeek V4 Pro vs GPT-5.5 for property and lettings admin
GPT-5.5 wins, 94–78
Same 12 property and lettings admin tasks, marked blind by three rival labs. GPT-5.5 took 9 tasks, DeepSeek V4 Pro took 0, 3 tied. Tested 18 Aug 2026.
Where they differed most
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.
On the first question: I cannot promise the landlord will definitely renew your tenancy after twelve months, because that decision is not mine to make. It belongs to the landlord, and they will decide based on their own circumstances and any factors at that time. What I can do is tell you honestly what I know about the landlord’s past practice and their current intentions, but I cannot bind them to a future commitment. A reasonable thing you could ask for instead is a longer fixed term now—for example, two years—or a tenancy agreement that incl…
**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
| Task | DeepSeek V4 Pro | GPT-5.5 |
|---|---|---|
| Two routes, one worried tenant | 8 | 10 |
| Six weeks late and hoping | 8 | 8 |
| Write only the arrears email | 8 | 10 |
| The pre-tenancy checklist | 9 | 9 |
| Write only the renewal reply | 10 | 10 |
| Three repairs, one Tuesday | 9 | 10 |
| The nine-year-old carpet | 6 | 8 |
| The rent rise by text message | 8 | 9 |
| Every claim in the advert must be true | 8 | 9 |
| The compliance data, as JSON | 6 | 10 |
| What the agent must not promise | 5 | 10 |
| Refuse the lock change | 9 | 10 |
Full receipts: DeepSeek V4 Pro, GPT-5.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, gpt-5.6-terra
Questions people ask
Which is better for property and lettings admin: DeepSeek V4 Pro or GPT-5.5?
GPT-5.5 — it scored 94/100 against 78/100 on our 12-task property and lettings admin suite, winning 9 tasks to 0 with 3 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 Opus 4.8 vs GPT-5.5 · Claude Fable 5 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · GPT-5.5 vs Grok 4.5
Full ranking: Best AI for property and lettings admin · model pages: DeepSeek V4 Pro, GPT-5.5