Gemini 3.5 Flash vs GPT-5.5 for bookkeeping
GPT-5.5 wins, 92–81
Same 12 bookkeeping tasks, marked blind by three rival labs. GPT-5.5 took 8 tasks, Gemini 3.5 Flash took 0, 4 tied. Tested 18 Aug 2026.
Where they differed most
Guidance excerpt: 'A VAT invoice must show: a sequential invoice number unique to that series; the supplier's name, address and VAT registration number; the customer's name and address; the date of issue and the time of supply where different; a description sufficient to identify the goods or services; the quantity, the unit price excluding VAT, the rate of VAT and the amount payable excluding VAT for each item; the total amount of VAT payable; and the rate of any cash discount offered.' Someone starting a mobile hairdressing business asks what the difference is between a quote, an invoice and a receipt, because she has been sending one document with 'Invoice/Quote' at the top. Explain each of the three: what it is, when it is issued, and what it does and does not commit her to. Then, using only the excerpt above and marked against it, set out what has to appear on her invoices once she is VAT registered, and say which of those items her current one-document-fits-all approach makes impossible.
Here is the explanation of the differences between the three documents, followed by the VAT invoice requirements and why your current "one-document-fits-all" approach will not work once you are VAT registered. --- ### Part 1: Quote vs. Invoice vs. Receipt #### 1. A Quote (or Quotation) * **What it is:** A formal offer showing the customer exactly how much the hairdressing service will cost before they agree to book it. * **When it is issued:** Before any work begins or any booking is confirmed. * **What it does/does not commit you to:…
You should use three different documents/labels, because they do different jobs. ## 1. Quote, invoice and receipt | Document | What it is | When issued | What it commits you to / does not commit you to | |---|---|---|---| | **Quote** | A proposed price for specified work, e.g. “cut and blow-dry at client’s home: £X”. | **Before** the customer decides to book or before the work is done. | If the customer accepts it, it can commit you to doing the described work for that quoted price, subject to any conditions you state, such as “valid for 30 d…
Task by task
| Task | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| The client lunch and the sandwich | 8 | 9.5 |
| Categorise, and admit what you cannot | 8 | 9 |
| The invoice totals | 10 | 10 |
| Find the £36 | 8 | 8 |
| Profit but no money | 8 | 9 |
| Not your decision to make | 8 | 9 |
| The faded shoebox | 7 | 9 |
| It is my company, it is my money | 8 | 8 |
| The mileage claim | 10 | 10 |
| Capital or revenue | 8 | 10 |
| Quote, invoice, receipt | 6 | 9 |
| Refuse the backdated invoice | 8 | 10 |
Full receipts: Gemini 3.5 Flash, GPT-5.5 · judges claude-sonnet-5, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for bookkeeping: Gemini 3.5 Flash or GPT-5.5?
GPT-5.5 — it scored 92/100 against 81/100 on our 12-task bookkeeping suite, winning 8 tasks to 0 with 4 tied. Every answer was marked blind by three judges from three rival AI labs.
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-5.5 vs GPT-5.6 Sol · Gemini 3.5 Flash vs GPT-5.6 Sol · GPT-5.5 vs Grok 4.5 · GPT-5.5 vs Kimi K3 · Claude Opus 4.8 vs GPT-5.5 · GLM 5.2 vs GPT-5.5
Full ranking: Best AI for bookkeeping · model pages: Gemini 3.5 Flash, GPT-5.5