GPT-5.3-Codex 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-5.3-Codex took 3, 6 tied. Tested 27 Aug 2026.
Where they differed most
The owner of a small events company rings, upset: her profit and loss for the quarter shows a profit of £4,180, but there is £900 in the business bank account and she has a VAT payment due. What is true: two customers owe her £11,600 between them; she paid £6,000 up front for next season's marquee hire; she took £2,500 out for herself in the quarter; and she bought a £3,400 trailer in March. Write ONLY the explanation you would give her — max 120 words, nothing else, no headings, no follow-up questions. Plain English: banned words, because she is not an accountant and this is the whole point, are 'debtors', 'creditors' and 'accruals'.
Your £4,180 profit is not the same as cash in the bank. It includes sales you’ve invoiced but not yet been paid for: £11,600 is still due from two customers. You also paid £6,000 in advance for next season’s marquee hire, which used cash now but is spread in the accounts over the time it covers. The £2,500 you took for yourself reduced bank cash but is not counted as a business running cost in the profit figure. And the £3,400 trailer is treated as equipment (a longer-term purchase), so it does not reduce profit all at once. So yes, you can sho…
The £4,180 profit is not the same as cash in the bank. It includes £11,600 of sales that your customers have not yet paid, so that money is not available for the VAT bill. You also paid £6,000 early for next season’s marquee hire; the cash has gone, but most or all of that cost will appear later. The £2,500 you took for yourself reduced the bank balance but does not reduce profit. Likewise, the £3,400 trailer used cash, but only its gradual loss in value is charged against profit. VAT collected from customers is also money owed to HMRC, not inc…
Task by task
| Task | GPT-5.3-Codex | GPT-5.6 Sol |
|---|---|---|
| The client lunch and the sandwich | 9 | 8 |
| Categorise, and admit what you cannot | 9 | 9 |
| The invoice totals | 10 | 10 |
| Find the £36 | 8 | 9 |
| Profit but no money | 10 | 8 |
| Not your decision to make | 10 | 10 |
| The faded shoebox | 8 | 10 |
| It is my company, it is my money | 9 | 8 |
| The mileage claim | 10 | 10 |
| Capital or revenue | 8 | 10 |
| Quote, invoice, receipt | 9 | 9 |
| Refuse the backdated invoice | 10 | 10 |
Full receipts: GPT-5.3-Codex, 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-5.3-Codex 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 GPT-5.6 Terra · GPT-5.3-Codex vs GPT-5.6 Terra · GPT-5.5 vs GPT-5.6 Sol · Claude Fable 5 vs GPT-5.6 Sol · GPT-5.6 Sol vs Grok 4.5 · GPT-5.6 Sol vs Qwen3.7 Max
Full ranking: Best AI for bookkeeping · model pages: GPT-5.3-Codex, GPT-5.6 Sol