Part 3: Using AI to see trouble coming · MODULE 14

A 13-week cash flow forecast with AI

A 13-week cash flow forecast shows your expected bank balance at the end of each week for the next quarter. You start with today's balance, add the money you expect from customers based on how they actually pay, and subtract wages, super, bills and BAS on their due dates. AI can build the table from your Xero exports in minutes. Your job is to check the assumptions.

8 MIN READ · UPDATED 10 OCTOBER 2026

IN THIS MODULE

Why 13 weeks
What goes into the forecast
A worked example
Building it with AI
Using the forecast
Common questions

Why forecast 13 weeks?

Thirteen weeks is one quarter, broken into weeks. That's long enough to see a BAS payment or a slow month coming, and short enough that your numbers are mostly real invoices and bills rather than guesses. Monthly forecasts hide the problem that hurts small businesses most: a single week where wages, a supplier and the ATO all fall due before a big customer pays.

EXAMPLE

A builder has paid a plumbing business for three years, usually about 18 days after invoice. Over the last three months the average has crept to 26 days, then 35. Nothing is badly overdue yet, so the total overdue figure barely moves.

The trend is the warning. A sensible response is to move the builder to 7-day terms on new work and ask for a deposit on the next big job, while the amount at risk is still small.

What goes into a cash flow forecast?

Money coming in

Your aged receivables from Xero, with each invoice placed in the week the customer is likely to pay. Use their usual payment habits, not the due date. A customer who usually pays 12 days late goes 12 days after the due date.
Work you'll invoice in the next 13 weeks, with realistic payment dates.
Deposits and progress payments you're expecting on current jobs.

Money going out

Wages on each payday.
Super with each payday. From 1 July 2026, Payday Super means employers pay super each pay cycle, and funds need to receive it within 7 business days of payday, rather than quarterly.
Supplier bills on their due dates, from your accounts payable in Xero.
BAS. Quarterly BAS is generally due on the 28th of the month after the quarter ends, except the December quarter, which is due on 28 February. Your tax agent may have later dates.
Rent, loan repayments, insurance, subscriptions and anything else that leaves on a schedule.

An example

Here are the first six weeks of a forecast for a small trade business with $18,000 in the bank, a weekly payroll of $6,500 plus 12% super, and a $9,600 BAS payment due in week 4:

Week 1:
- Money in: $9,500
- Money out: $10,280
- Expenses: Wages and super, rent
- Closing balance: $17,220
Week 2:
- Money in: $6,200
- Money out: $11,780
- Expenses: Wages and super, supplier
- Closing balance: $11,640
Week 3:
- Money in: $12,800
- Money out: $7,280
- Expenses: Wages and super
- Closing balance: $17,160
Week 4:
- Money in: $4,100
- Money out: $23,680
- Expenses: Wages and super, supplier, BAS
- Closing balance: −$2,420
Week 5:
- Money in: $8,900
- Money out: $10,280
- Expenses: Wages and super, rent
- Closing balance: −$3,800
Week 6:
- Money in: $11,300
- Money out: $11,180
- Expenses: Wages and super, supplier
- Closing balance: −$3,680

What the forecast tells you

The business is profitable, but the bank account goes negative in week 4 because the BAS and a $6,800 supplier bill land in the same week as a quiet week for receipts. Seeing it four weeks out gives time to act.

The forecast doesn't expect a $9,000 overdue invoice until week 9, because that customer usually pays late. Following it up now and getting it paid before week 4 keeps the balance positive through all six weeks. Moving the supplier bill alone wouldn't be enough, because the shortfall carries into week 5.

What goes into a cash flow forecast?

Money coming in

Your aged receivables from Xero, with each invoice placed in the week the customer is likely to pay. Use their usual payment habits, not the due date. A customer who usually pays 12 days late goes 12 days after the due date.
Work you'll invoice in the next 13 weeks, with realistic payment dates.
Deposits and progress payments you're expecting on current jobs.

Money going out

Wages on each payday.
Super with each payday. From 1 July 2026, Payday Super means employers pay super each pay cycle, and funds need to receive it within 7 business days of payday, rather than quarterly.
Supplier bills on their due dates, from your accounts payable in Xero.
BAS. Quarterly BAS is generally due on the 28th of the month after the quarter ends, except the December quarter, which is due on 28 February. Your tax agent may have later dates.
Rent, loan repayments, insurance, subscriptions and anything else that leaves on a schedule.

An example

Here are the first six weeks of a forecast for a small trade business with $18,000 in the bank, a weekly payroll of $6,500 plus 12% super, and a $9,600 BAS payment due in week 4:

Week 1:
- Money in: $9,500
- Money out: $10,280
- Expenses: Wages and super, rent
- Closing balance: $17,220
Week 2:
- Money in: $6,200
- Money out: $11,780
- Expenses: Wages and super, supplier
- Closing balance: $11,640
Week 3:
- Money in: $12,800
- Money out: $7,280
- Expenses: Wages and super
- Closing balance: $17,160
Week 4:
- Money in: $4,100
- Money out: $23,680
- Expenses: Wages and super, supplier, BAS
- Closing balance: −$2,420
Week 5:
- Money in: $8,900
- Money out: $10,280
- Expenses: Wages and super, rent
- Closing balance: −$3,800
Week 6:
- Money in: $11,300
- Money out: $11,180
- Expenses: Wages and super, supplier
- Closing balance: −$3,680

What the forecast tells you

Building the forecast with AI

Export your aged receivables (aged by due date), your aged payables and your upcoming payroll from Xero. Replace customer and supplier names with codes. Then use this prompt.

AI PROMPT

I run a small business in Australia. Build a 13-week cash flow forecast starting [date].

My bank balance today is $[amount].
Payroll: $[amount] every [week / fortnight] on [day], plus [12]% super paid with each payday.
BAS: about $[amount] due on [date].
Other regular payments: [rent, loans, insurance, with amounts and dates].

Below are my aged receivables (customer names replaced with codes) and my upcoming bills.

Place each receivable in the week the customer is likely to pay. Use these habits: [for example, C01 usually pays 10 days late; everyone else pays within a week of the due date].
Add the outgoings on their due dates.
Show a table with week, money in, money out, what's going out and closing balance.
Flag any week where the balance drops below $[minimum].
For each flagged week, list the receivables that would fix it if they arrived earlier.
List your assumptions so I can check them.

[Paste aged receivables]
[Paste upcoming bills]

Check the totals against Xero before you rely on it, and ask the AI to show its working if anything looks off. AI tools can make arithmetic mistakes on long tables.

Using the forecast each week

Update it every Monday with the actual bank balance and anything that's been paid.
Roll it forward one week, so you always see 13 weeks ahead.
Look first at the lowest balance in the next six weeks. That's the number that tells you whether to act.
Compare what customers actually paid with what you forecast. If the same customer is always late, adjust their habit in the prompt.

The forecast is also the best argument for following up early. When you can see that one $9,000 invoice is the difference between a positive balance and an overdraft, the call stops feeling awkward.

Step 1: Export the data from Xero

Open the Aged Receivables Summary report. Set it to age by due date, so the columns show how overdue each balance is, rather than how old the invoice is.
Export it to Excel or Google Sheets, then save it as a CSV file.
For trends, also export your sales invoices from the last 12 months with invoice date, due date, paid date, amount and contact.

The aged receivables summary tells you where things stand today. The invoice history tells you which way each customer is heading, which is usually the more useful of the two.

Step 1: Export the data from Xero

Open the Aged Receivables Summary report. Set it to age by due date, so the columns show how overdue each balance is, rather than how old the invoice is.
Export it to Excel or Google Sheets, then save it as a CSV file.
For trends, also export your sales invoices from the last 12 months with invoice date, due date, paid date, amount and contact.

The aged receivables summary tells you where things stand today. The invoice history tells you which way each customer is heading, which is usually the more useful of the two.

Common questions

What is a 13-week cash flow forecast?

A 13-week cash flow forecast shows your expected bank balance at the end of each week for the next quarter. It combines money you expect from customers, based on how they usually pay, with wages, super, bills and tax on their due dates, so you can see cash shortfalls weeks before they happen.

Can AI build a cash flow forecast from Xero?

Yes. Export your aged receivables, aged payables and payroll details from Xero, replace names with codes, and ask an AI tool to place each item in the week it's likely to land. Check the totals against Xero and review the assumptions, because AI can make arithmetic mistakes.

How does Payday Super affect cash flow?

From 1 July 2026, employers pay super with each pay cycle instead of quarterly, and funds need to receive it within 7 business days of payday. That spreads the cost more evenly, but it means super now comes out of your account every payday, so your forecast should show it alongside wages.