Claude Opus 4.8 vs DeepSeek V4 Pro for property and lettings admin

The verdict

Claude Opus 4.8 wins, 8978

Same 12 property and lettings admin tasks, marked blind by three rival labs. Claude Opus 4.8 took 8 tasks, DeepSeek V4 Pro took 1, 3 tied. Tested 18 Aug 2026.

Where they differed most

The task — The compliance data, as JSON

Messy notes from a portfolio handover, exactly as written: '14 Ashworth Rd, Leeds LS6 - gas cert done 3rd March 26, EPC band C, deposit £1150 with TDS, ref TDS-88421, EICR I think 2023 but no paperwork. Flat 2, 88 Marine Parade, Brighton - EPC D, gas cert 12/11/2025, no deposit taken (company let), EICR Feb 2024. 7 Cwmbran Close - all electric so no gas cert needed, EPC band B, deposit £900 DPS ref unknown, EICR done last month.' Reply with ONLY valid JSON — no prose before or after. An array of three objects, in the order the properties appear, each with exactly these keys and no others: address (string, as written in the notes), epc_band (string, a single uppercase letter, or null if not stated), gas_certificate_date (string in YYYY-MM-DD form, or null if not stated or not applicable), eicr_date (string in YYYY-MM-DD form, or null if the notes do not give a full date), deposit_gbp (number, or null if no deposit), deposit_scheme (string, or null), deposit_reference (string, or null), needs_chasing (an array of strings naming each item on that property you would have to chase before you could rely on this record).

[
  {
    "address": "14 Ashworth Rd, Leeds LS6",
    "epc_band": "C",
    "gas_certificate_date": "2026-03-03",
    "eicr_date": null,
    "deposit_gbp": 1150,
    "deposit_scheme": "TDS",
    "deposit_reference": "TDS-88421",
    "needs_chasing": ["EICR certificate and date"]
  },
  {
    "address": "Flat 2, 88 Marine Parade, Brighton",
    "epc_band": "D",
    "gas_certificate_date": "2025-11-12",
    "eicr_date": null,
    "deposit_gbp": null,
    "deposit_scheme": null,
    "deposit_reference": null,
    "needs_chasing": ["exact EICR date…
[
  {
    "address": "14 Ashworth Rd, Leeds LS6",
    "epc_band": "C",
    "gas_certificate_date": "2026-03-03",
    "eicr_date": null,
    "deposit_gbp": 1150,
    "deposit_scheme": "TDS",
    "deposit_reference": "TDS-88421",
    "needs_chasing": ["gas safety certificate", "EICR certificate"]
  },
  {
    "address": "Flat 2, 88 Marine Parade, Brighton",
    "epc_band": "D",
    "gas_certificate_date": "2025-11-12",
    "eicr_date": null,
    "deposit_gbp": null,
    "deposit_scheme": null,
    "deposit_reference": null,
    "needs_chasing": […

Task by task

TaskClaude Opus 4.8DeepSeek V4 Pro
Two routes, one worried tenant98
Six weeks late and hoping98
Write only the arrears email108
The pre-tenancy checklist99
Write only the renewal reply1010
Three repairs, one Tuesday89
The nine-year-old carpet86
The rent rise by text message108
Every claim in the advert must be true98
The compliance data, as JSON106
What the agent must not promise55
Refuse the lock change109

Full receipts: Claude Opus 4.8, DeepSeek V4 Pro · 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 DeepSeek V4 Pro?

Claude Opus 4.8 — it scored 89/100 against 78/100 on our 12-task property and lettings admin suite, winning 8 tasks to 1 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: Claude Opus 4.8 vs GPT-5.5 · DeepSeek V4 Pro vs GPT-5.5 · Claude Opus 4.8 vs GPT-5.6 Sol · DeepSeek V4 Pro vs GPT-5.6 Sol · Claude Opus 4.8 vs Kimi K3 · DeepSeek V4 Pro vs Kimi K3

Full ranking: Best AI for property and lettings admin · model pages: Claude Opus 4.8, DeepSeek V4 Pro