GPT-5.5 vs GPT-5.6 Sol for bookkeeping
Effectively a dead heat: 93–92
Same 12 bookkeeping tasks, marked blind by three rival labs. GPT-5.6 Sol took 3 tasks, GPT-5.5 took 2, 7 tied. Tested 18 Aug 2026.
Where they differed most
Guidance excerpt: 'VAT incurred on business entertainment provided to people who are not employees cannot normally be reclaimed as input tax. VAT on subsistence — reasonable meals and drinks for employees, or for the business owner, while travelling on business — can normally be reclaimed if you hold a valid VAT invoice. Where one bill covers both employees and non-employees, only the employee element may be reclaimed. A card receipt that does not show the supplier VAT number is not a valid VAT invoice.' The situation: Ray runs a VAT-registered building firm. In March he has two receipts. One is £86.40 for lunch with a prospective client, at which he also ate; it is a card slip with no VAT number on it. The other is £14.20 for his own sandwich and coffee at a motorway services on the way to a site 90 miles away, with a full VAT receipt. Answer using only the excerpt above — your answer is marked against that excerpt, not against outside knowledge. Take each receipt in turn, say what happens to the VAT and to the cost itself in the books, and say plainly which point here is one to put to his accountant rather than settle from the excerpt.
Using only the excerpt: ### 1) £86.40 lunch with prospective client, Ray also ate — card slip, no VAT number - **VAT:** Do **not** reclaim any VAT. Reasons from the excerpt: - It is business entertainment for a **non-employee** prospective client, and VAT on that cannot normally be reclaimed. - The card slip has **no supplier VAT number**, so it is **not a valid VAT invoice** anyway. - **Cost in the books:** Enter the **full £86.40 gross cost** as a cost, with **no input VAT split out/reclaimed**. It would naturally be recorded as cli…
- **£86.40 lunch with prospective client:** The card slip is not a valid VAT invoice because it lacks the supplier’s VAT number, so **no VAT can be reclaimed**. The entire **£86.40 should therefore be recorded gross as a business-entertainment cost**. Even with a valid invoice, the prospective client’s element would normally be blocked. Whether Ray’s own share should be separated, and whether any of this entertainment cost is deductible for direct-tax purposes, is **a point for his accountant**, since the excerpt deals only with VAT. - **£14.2…
Task by task
| Task | GPT-5.5 | GPT-5.6 Sol |
|---|---|---|
| The client lunch and the sandwich | 9.5 | 8 |
| Categorise, and admit what you cannot | 9 | 9 |
| The invoice totals | 10 | 10 |
| Find the £36 | 8 | 9 |
| Profit but no money | 9 | 8 |
| Not your decision to make | 9 | 10 |
| The faded shoebox | 9 | 10 |
| It is my company, it is my money | 8 | 8 |
| The mileage claim | 10 | 10 |
| Capital or revenue | 10 | 10 |
| Quote, invoice, receipt | 9 | 9 |
| Refuse the backdated invoice | 10 | 10 |
Full receipts: GPT-5.5, GPT-5.6 Sol · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for bookkeeping: GPT-5.5 or GPT-5.6 Sol?
Effectively a dead heat: GPT-5.6 Sol edged it 93/100 to 92/100 on our bookkeeping suite — too close to matter, so pick on price or the product you already use.
How was this tested?
Both models answered the identical published bookkeeping 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 bookkeeping head-to-heads: GPT-5.6 Sol vs Grok 4.5 · GPT-5.6 Sol vs Kimi K3 · Claude Opus 4.8 vs GPT-5.6 Sol · GLM 5.2 vs GPT-5.6 Sol · Claude Sonnet 5 vs GPT-5.6 Sol · Gemini 3.5 Flash vs GPT-5.6 Sol
Full ranking: Best AI for bookkeeping · model pages: GPT-5.5, GPT-5.6 Sol