You can build an internal settlement date calculator for your conveyancing practice in an afternoon using Claude Artifacts or ChatGPT Canvas — no developer and no code you need to understand. You describe the tool in plain English: contract date in; cooling-off expiry, finance date and settlement date out, counted in business days and aware of your state's public holidays. The AI writes a working one-page calculator you can open in a browser. The catch, and it matters, is that every rule the calculator applies must be an input your firm sets and verifies — not a fact the AI invents — and every output needs a human check before anyone relies on it.
This guide is for Australian conveyancers, settlement agents and conveyancing support staff who do the same date arithmetic by hand every week and want a faster, more consistent way to do the first pass. It is not legal advice, and the tool you build is not either.
What the calculator should do — and what it must not
The job is narrow on purpose. You enter a contract date and a few options, and the tool returns the key dates a matter hangs on. That is a maths task, and AI is good at maths tasks with clear rules.
A sensible first build takes these inputs and produces these outputs:
| Inputs you enter | Outputs it calculates |
|---|---|
| Contract date | Cooling-off expiry date |
| State (QLD, NSW, VIC, etc.) | Finance approval due date |
| Cooling-off period (business or calendar days) | Building and pest due date |
| Finance clause period | Settlement date |
| Settlement period | A plain list showing each date and how it was counted |
What it must not be: a source of truth about what the cooling-off or finance periods actually are, a client-facing page on your website, or anything that goes into a contract or client email without a person checking it. It is a calculator you drive, not an adviser. Treat its output the way you would treat a junior's first draft — useful, and always checked.
Why state cooling-off periods must be inputs, not hardcoded
Cooling-off rules differ by state and by the type of sale, and they change. If you ask the AI to "bake in the QLD cooling-off period" you are trusting a general-purpose model to state a legal period correctly — and to keep it correct forever. It will not, and you should not build on that.
So the rule for a reliable cooling-off period calculator across QLD, NSW and VIC is simple: the period is a field the conveyancer fills in, with a dropdown for whether it counts business days or calendar days, and whether it excludes the contract date. Your firm sets the number from the current legislation and your own precedents; the calculator only does the counting. That way the tool survives a rule change — you update one field, not a line of code you cannot read.
Build it so the state dropdown pre-fills a suggested period you can still edit, and label that suggestion clearly as "check against current rules". The person using it stays responsible for the number. That is the honest design, and it is also the one that keeps you out of trouble.
How to build it in Claude Artifacts, step by step
Claude Artifacts is the easiest place to start because it shows the working calculator next to the chat, so you see changes as you make them. Go to claude.ai, sign in (the free tier is enough for a first build; the paid Pro tier gives you more room to iterate), start a new chat and paste this:
"Build a single-page settlement date calculator for an Australian conveyancing firm, as an interactive artifact. Inputs: a contract date picker; a state dropdown (QLD, NSW, VIC, SA, WA, TAS, ACT, NT); a cooling-off period as a number with a dropdown for business days or calendar days; a finance period (number of days); a building-and-pest period (number of days); and a settlement period (number of days). For each period let me choose whether the count excludes the contract date. Output a clear table showing each resulting date and the day of the week. Don't hardcode any legal periods — leave every period as a field I fill in."
Claude will generate a calculator on the right. Enter a test contract date and some periods, and check the dates by hand against a calendar. If something is off, you fix it by describing the problem — not by editing code.
The same build works in ChatGPT Canvas: start a chat, ask for "an interactive HTML settlement date calculator" with the same brief, and ChatGPT opens it in the Canvas side panel. If you want background on how this plain-English building works, our explainer on what vibe coding is for business owners covers the mindset.
Making it a business days calculator with public holidays
Counting business days is where hand calculations go wrong, because you have to skip weekends and public holidays — and public holidays differ by state. This is exactly what a calculator should own. Follow up with:
"When a period is set to business days, skip Saturdays, Sundays and public holidays for the selected state. Let me paste in a list of public holiday dates for the current and next year, so I control the list rather than relying on built-in data. If a calculated date lands on a weekend or a holiday, show both the raw date and the next business day, and label which is which."
Notice the design choice: you paste the holiday list. Do not let the AI generate public holiday dates from memory — they shift each year, states gazette their own, and a wrong Ekka or Labour Day date quietly corrupts every count. Copy the official dates from your state government's public holidays page into the tool once a year. A business days calculator with public holidays is only as good as the list you feed it, so own the list.
Add one more instruction so nothing silently rolls: "If settlement lands on a weekend or holiday, flag it in red and show the next business day, but don't change it automatically — I'll decide."
What to do when the first result is wrong
The first version will get something wrong, and reacting to that is the actual skill. The fix is always a plain-English correction, tested against a case you already know the answer to. Common early failures and what to type back:
- Off-by-one counting. "For the finance period, day one should be the day after the contract date, not the contract date itself. Recalculate and show me the count for a 14-day period from a Monday."
- Weekends not skipped. "The building-and-pest date landed on a Sunday. For business-day periods, weekends must not count. Walk me through how you counted this one."
- Holidays ignored. "Easter Monday is in my pasted holiday list but the count included it. Exclude every date in that list."
- Dates in US format. "Show all dates as DD/MM/YYYY and the day name, Australian format."
Test with at least three real-looking scenarios — one that crosses a weekend, one that crosses a public holiday, and one that crosses the end of a month — and confirm each by hand before you trust the tool for anything. If it passes those, it will handle the routine cases. Our rundown of vibe coding risks for professional services firms explains why this test-against-known-answers habit is non-negotiable.
The human-check step is part of the tool
Build the check into the interface so it cannot be skipped. Ask for a line at the bottom of every result:
"Add a note under the results that reads: 'Calculated estimate only — verify every date against the contract and current state rules before relying on it.' Add a checkbox labelled 'Checked by' with a name field, and don't let the dates be copied until it's ticked."
That friction is deliberate. The calculator removes the arithmetic, not the professional judgement. A date that is right 99 times and wrong once is more dangerous than a manual process, because people stop checking. Keep the human in the loop and the tool stays an asset. This is a first-pass accelerator that sits alongside, not instead of, the broader settlement workflow automation covered in our conveyancers guide.
Keeping it internal — and out of shadow IT
This tool is for conveyancing staff only. Do not put it on your website or send clients a link. The moment it is client-facing, a wrong date becomes something a client acted on, and you have no review step. Internal tools for conveyancing staff should live somewhere controlled and known to the firm.
On privacy: a date calculator does not need any personal information. Keep it that way — enter a contract date and periods, never a client name, address or matter details. The OAIC's general guidance on commercially available AI products is that publicly available chatbots should not be given personal information, and the Privacy Act applies the moment you do. A pure calculator sidesteps the issue entirely, which is another reason to keep its scope narrow. If your workflow ever starts feeding real matter data into AI tools, read our note on AI and client data under the Australian Privacy Act first.
On ownership: a Claude Artifact or ChatGPT Canvas lives in that account. Decide who owns it, save a copy of the generated file somewhere the firm controls, and record it in your AI policy so it is a sanctioned tool rather than one admin's private shortcut. When the AI product updates, re-run your three test scenarios to confirm nothing drifted. If the calculator ever needs logins, to pull from your practice management system, or to handle payments, that is the point to stop and bring in a developer — it has outgrown a vibe-coded afternoon.
If you want more ready-made starting points for this profession, our collection of ChatGPT prompts for conveyancers pairs well with a calculator like this.
A date calculator is one small job among many that eats a conveyancer's week. If you want a shortlist of the others worth automating first, download our free guide, 10 AI Workflows to Save 10+ Hours a Week — it will help you decide what to build next and what to leave alone.
Common questions
Should the cooling-off period be built into the calculator?
No. Make it a field the conveyancer enters and verifies, with a dropdown for business or calendar days. Cooling-off periods differ by state and sale type and change over time. If you hardcode them, a rule change silently breaks the tool. Setting the number as an input means you update one field and the calculator keeps counting correctly.
How does the calculator handle public holidays correctly?
Paste in the official public holiday dates for your state yourself, once a year, rather than letting the AI generate them from memory. Gazetted holidays vary by state and shift annually, so a model-generated list will eventually be wrong. The tool then skips weekends and the dates in your pasted list when counting business days, and flags any result that lands on one.
Is Claude Artifacts or ChatGPT Canvas better for building this?
Both work and the free tiers are enough to start. Claude Artifacts shows the working calculator beside the chat, which makes iterating easy. ChatGPT Canvas does the same in a side panel. Pick whichever you already have access to, give it the same plain-English brief, and test the output against dates you already know by hand.
Can I let clients use this settlement date calculator?
No. Keep it strictly internal. The tool produces estimates that need a professional check before anyone relies on them, and there is no review step once a client acts on a link. Build in a mandatory 'checked by' step, keep it off your website, and record it in your firm's AI policy as a sanctioned internal tool.
Does a date calculator raise privacy concerns under the Privacy Act?
Not if you keep it to dates and periods only, with no client names, addresses or matter details. The OAIC's general guidance is that publicly available AI chatbots should not be given personal information, and the Privacy Act applies the moment you do. A calculator that only takes a contract date and clause periods avoids the issue entirely, which is a good reason to keep its scope narrow.
Want these ideas working in your firm? We build controlled AI workflows for Australian professional services firms — starting with a free automation audit.