Business Australia
Invoice Due Date Calculator Australia
Payment terms such as net 30 or 30 days end of month mean different dates, and a due date that falls on a weekend can slip to Monday. Enter the invoice date and the terms to see the due date, the weekday it falls on and how many days are left.
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Due date
—Weekday
—
Days after the invoice date
—
Days from today
—
If the weekend rule is off
—
The working
Check your terms. General information and estimates only, not professional advice. Your contract or invoice terms decide the due date.
How do I work out an invoice due date?
Add the number of days in the payment terms to the invoice date. An invoice dated Thursday 12 November 2026 on 30-day terms is due on Saturday 12 December 2026. Under 30 days end of month terms the 30 days start from the end of the invoice month, so the due date is later.
Choosing payment terms
Shorter terms get you paid sooner and help your cash flow. Thirty days is a common standard, but some customers, especially large organisations, ask for 45 or 60 days. Consider offering a small early-payment discount, and be clear about late fees. Ask new customers for a deposit or payment upfront if you do not know them.
Getting paid
Put the due date, amount, bank details and a payment reference on every invoice. Send it as soon as the work is done and follow up politely the day after it is due. A phone call often works better than another email. For regular late payers, shorten the terms or ask for payment upfront.
To create an invoice, use the tax invoice generator.
How this is calculated
The rule, step by step, so you can check any figure by hand.
net N days: due date = invoice date + N daysN days end of month: due date = the last day of the invoice month + N daysdue on receipt: due date = invoice dateweekend rule: if the due date is a Saturday or Sunday, move it to the next Monday
'End of month' terms start the clock at the end of the month in which the invoice is dated, so an invoice dated early in the month gets nearly an extra month to be paid. A supplier who bills on the first of the month and offers 30 days end of month is effectively giving 60 days.
Public holidays are not moved by this calculator, only weekends. If a due date falls on a public holiday, many businesses treat the next working day as the date, but your contract decides. Put the exact due date on the invoice to avoid arguments.
A worked example
An invoice dated Thursday 12 November 2026, 30-day terms.
- Due dateSaturday 12 December 2026
- Weekend moved toMonday 14 December 2026
- Days after the invoice date30
- With 30 days end of month30 December 2026
Due Monday 14 December.
Write the exact date on the invoice.
Cash flow
Every extra day you wait to be paid is a day you fund your customer. If you have bills due before your invoices, use the due date to plan, and keep a cash buffer.
What it leaves out
Public holidays, interest on late payment and bank processing time are not modelled. Allow a day or two for a payment to arrive.
What this calculator does not do
- Calendar days
- Weekend rule only, no public holidays
- Your contract decides
- General information
Common questions
What does net 30 mean?
Payment is due 30 days after the invoice date.
What does 30 days end of month mean?
Thirty days counted from the end of the invoice month.
What if the due date is a weekend?
Many businesses accept the next working day; check your terms.
Can I charge for late payment?
Only if your agreement says so; put it in writing.
Should I put the due date on the invoice?
Yes, the exact date.
Where these numbers come from
- business.gov.au — invoicing Government guidance on invoices and getting paid
Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.
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