Fiscari vs ChatGPT

ChatGPT for UK tax: why it is not enough

Fiscari retrieves from a fixed corpus of UK primary sources, cites the paragraph, and refuses when it cannot ground an answer. Here is why that matters for tax work — and where ChatGPT is still the better tool.

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Where Fiscari is stronger

General-purpose AI is genuinely remarkable, and for tax research it is the wrong shape. Not because the model is weak, but because of what it is allowed to see and what it is obliged to do when it does not know. Prompting cannot fix either.

A fixed corpus, not the open web

Answers are retrieved from indexed UK legislation, HMRC manuals, VAT notices and tribunal decisions. The section numbers in an answer are the ones in the retrieved text, so they cannot be invented.

Citations you can click

Every answer deep-links to the paragraph it rests on. Ask a general model for "the specific section" and you get something shaped like a citation, which you then have to verify yourself — at which point it has not saved you time.

Current guidance, not a training snapshot

Manuals get updated, VAT notices revised, Briefs superseded. A general model can only recall the web as it was at its training cut-off; it cannot retrieve the live paragraph.

It refuses when it cannot ground

Professional research needs a tool that knows when it does not know. General AI is trained to answer everything with roughly uniform confidence, whether or not it is qualified to.

Head to head

	Fiscari	ChatGPT
Source scope	A fixed corpus of UK primary sources	Open web training data
How answers are produced	Retrieved from indexed sources, then generated	Generated from training memory
Citations	Deep-linked to the paragraph	Often vague, sometimes fabricated
Currency of guidance	Corpus refreshed on a schedule	Fixed at the training cut-off
Refuses when ungrounded	Yes — published policy	No — always answers
Defensible for client work	Yes — every claim is checkable	No

Compiled from each vendor's own published material, August 2026. Third-party prices and accuracy figures are those vendors' own published figures. Confirm current terms with the vendor.

Straight about the limits

What Fiscari cannot do

Three things worth knowing before you switch, including the cases where ChatGPT is the better buy.

We only do UK tax

Fiscari will not draft your client email, summarise a document you paste in, write a proposal, or answer anything outside UK tax. ChatGPT does all of that well. Most firms should use both, for different jobs.
Narrow by design

The corpus is deliberately limited to public UK primary sources. That is what makes an answer defensible, and it also means no commentary, no worked examples from practitioners, and nothing outside the UK.
It is not free

ChatGPT has a free tier and we do not pretend to compete with that on price. What you are paying for is a citation you can put in a file note.

Worth a look if…

You have already been caught out

If you have seen a confident answer cite a section that turned out not to exist, you already understand the problem this solves.
You are verifying every answer by hand

If the workflow is ask, then check on legislation.gov.uk, the AI is adding a step rather than removing one.
The answer has to survive review

Peer review, a client challenge, or an HMRC enquiry all need a source you can point at.