It’s month end, and three people in your accounts team are each asking ChatGPT to draft the email chasing a customer’s overdue invoice.

Each wrote their own prompt. One gets a friendly email that forgets the due date. Another chases a customer for an invoice they paid last week. You find out when the customer rings, irritated, and asks for the managing director, which is you.

Left alone, your team spends the hours it meant to save rewriting drafts, and customers wonder whether anyone checks their account before chasing. Here’s a five-part brief anyone can use, and a way to test it on last month’s work.

Draw the boundary around one job

Start with the job as it runs today. Name the event that starts it, what goes in, what should come out, who checks it and what happens next.

For the overdue invoice email, it might read like this. The month-end list of overdue invoices triggers it. The list, the customer’s name and any payments or replies since the last reminder go in. A draft email comes out. The accounts assistant who looks after that customer checks it, then sends it from their own inbox.

Keep the job narrow enough to describe without adding exceptions halfway through the sentence. Drafting the overdue invoice email is a job. Handling customer communication is a department. Coding supplier invoices is a job. Running the month-end close is several jobs.

The boundary tells the tool what it mustn’t do as clearly as what it should. If the job ends when a draft reaches the accounts assistant, say so. The tool doesn’t send the email, mark anything as paid or change the customer’s account. Those actions sit outside the brief, and the accounts assistant knows exactly where their part starts.

Name the rules and where each comes from

With the boundary fixed, add the rules that govern the work. Start with material the business already relies on: your standard reminder wording, the payment terms you give customers, and anything customers must never be asked, such as their card details.

Name the trusted source for each rule. If the due date comes from the invoice and your terms, say so. If payments come from the latest bank feed, point the tool at it and tell it not to chase anything already paid. The tool needs the same clear source a new starter would need in their first week.

Your written material won’t hold every decision an experienced person in accounts makes. One customer always pays on the last Friday of the month. Another’s director has agreed a payment plan by phone. That’s why getting the unwritten rules out of one person’s head comes first, whatever the job. Write each one as a condition and an action, and keep the reason beside it for whoever maintains the brief.

The source material needs the same care. Preparing documents for AI means one current copy of each file, consistent terms and clear limits on what the tool can reach. A precise brief can’t rescue contradictory reference material. And only run this in a tool your business has approved for customer financial data. If you haven’t settled that yet, what happens to client data you paste into AI comes before the brief.

Describe a good output as visible checks

Now describe what the draft must contain. Avoid asking for something accurate, professional or clear. Those words sound sensible, but they don’t tell the accounts assistant what to compare.

Name the parts instead. A good reminder email lists every overdue invoice with its number, date and amount, exactly as on the list. It chases nothing already paid. It states the due date and says what the customer should do next: pay, send a remittance or tell you about a dispute.

Then write the review test beside that description. The accounts assistant should be able to hold the draft against the list and tick four things in under a minute. If checking means rebuilding the whole email from scratch, the brief has moved the effort rather than removed it.

The standard belongs to the people who write, check and answer for the work. Agreeing what good looks like with them before launch gives the brief a standard that holds up on the busiest day of month-end.

Tell the tool to stop, not guess

Every brief reaches a point where the source doesn’t hold the answer, two rules conflict or the input sits outside the boundary. Decide what happens in advance.

Stop and hand the item to a person. The handover needs a destination, not just the word “escalate”. Leave the draft unfinished, mark the invoice the tool couldn’t handle, and name the source that didn’t answer it. The accounts assistant picks it up from there.

I believe a clean handover is worth more than a clever guess. That handover counts as a good output. A tool that stops on an invoice for a clear reason has done its job properly. It has kept a plausible guess away from a customer who’d have spotted it.

Don’t hide uncertainty behind softer wording. “Make your best attempt” still asks the tool to guess. “Mention anything you’re unsure of at the end” still leaves the accounts assistant with an email that may get sent. Stop first, say why, then hand over.

Test the brief on last month’s reminders

The first version of the brief is a draft until it has met real material. Test it on last month’s overdue lists, including the awkward customers your most experienced person in accounts handles differently.

Run each list through the brief and compare the draft with the email that went out. Where they differ, work out whether the brief missed a rule, pointed at the wrong source or described the output too loosely. Change the brief, then run the same list again. That isn’t teaching the tool the answer. It’s checking whether the written instruction now handles a case the business already understands.

Watch the handovers closely. If the tool guesses where it should stop, tighten the stop rule. If it stops on ordinary invoices, a rule or the boundary is too vague.

Suppose each accounts assistant looks after 25 customers and spends 10 minutes fixing each draft. That’s about 4 hours a month per person, which is the number the test should bring down. Keep the test record with the brief so the next person can see what it has already faced.

Keep one brief, with an owner

Once the test holds, store the brief beside the job it controls. Give it one owner, a review date and a single current version. Three people with three private copies is where you started. A copy saved in a separate folder drifts away from the work as soon as somebody changes a due date or a template.

Update the brief when the job changes, such as new payment terms, a new reminder template or a new customer rule. Don’t update it every time the tool produces a surprising draft that still sits within the rules. The brief describes a decision the business has made. It shouldn’t bend around every individual output.

Whoever owns the job decides when the brief changes and tells the others. In a business your size, that’s usually whoever runs accounts day to day, with you signing off anything that touches what customers are told.

Write the brief with your best person in accounts

This week, book 2 hours with the person in accounts whose reminders customers pay fastest. Bring last month’s overdue lists for five customers and the emails that went out.

In the first hour, write the five parts together: the boundary, the rules, the source for each rule, the output checks and the stop rule. In the second, run the five lists through the brief and fix what the comparison shows.

Next month, have everyone in accounts use that one brief, and put a 30-minute review in the diary after month-end to change it once, together.