AP automation ROI calculator: what automating invoice approval is worth
Automating invoice approval can give your team hours back and stop money leaking on bills nobody should pay, while a named person still approves each one.
Renzo Demartini, Chartered Accountant and finance executive · · 5 min read Drafted with AI, reviewed and spot-checked by me.
Exhibit 1Should this supplier bill reach the pay run?
Supplier bill INV-40817
Sample, incl. GST
Total
A$1,859.88
Order
PO-1182
Status
ReceivedHeldWith a person
Duplicate checkNumber, supplier, amountNo earlier match
Match to the orderPrice, quantity, goods receivedHangers 12% over
Accounts lead decidesWithin their delegationNeeds a decision
A supplier bill arrives against order PO-1182. It looks routine.
Joist hangers are A$48.90 a box against A$43.60 on the order: A$69.96 more.
A person decides: approve, query the supplier or reject. Nothing is paid yet.
A$69.96 over the order is held for a person to decide, and payment stays a separate step.
Illustrative figures, not client data.
In short
The case rests on two numbers: hours back for your team, which is capacity, and money kept from duplicates and price creep, which is cash.
Done well, controls get stronger: rules check every bill, a person within their delegation approves it and payment stays a separate step.
Size it with your own figures in the calculator, including what it costs to run, then ask your team for a baseline month before you decide how far to go.
AP automation ROI comes from two numbers: the hours your team gets back and the money kept from bills nobody should pay. The calculator on this page sizes both with your own figures.
Every supplier bill passes through several hands before the money leaves. Each handover costs time. Some cost money: a bill paid twice, a price nobody agreed, goods that never arrived.
Since 2023 I have automated payroll, AP and the month-end, removing more than 500 labour hours a year. Results from past roles aren’t a promise of what will happen in yours.
What it saves: two numbers, not one
Exhibit 2
Hours back are capacity and money kept is cash: count them apart
Hours back
Less keying, chasing and checking by hand
Capacity, not cash
Becomes money only if the time goes to work worth doing, or saves a hire
Money kept
Duplicates, price creep and bills for goods never received
Stopped before they are paid
Cash, and usually the harder number
Exhibit 3 · Try itWhat it could save your businessStart with the sample bill to see what the guards catch. Then enter your own monthly figures and switch between Cautious and Typical to see the hours back, the money kept and how much rides on the assumptions.Open the calculator ↓Close ↑
Sample supplier and illustrative figures. A planning estimate from your own inputs and the assumptions shown, not a quote or a promise of savings. The running-cost figure starts at A$400 a month, the sample in the cost-to-own calculator; enter your own quotes for the workflow software, AI model use and any support. Hours are time and the money kept is cash: they are shown apart. Nothing you enter leaves your browser.
The calculator sizes both from five figures in a typical month: bills, minutes per bill, the share with a problem, the average bill and the hourly cost of the person doing the work. Count active minutes only, not time in a queue.
Cautious assumes 40% of handling time goes and the guards stop 70% of today’s problems. Typical assumes 60% and 85%. Neither is a measured result. If the case only works on Typical, it isn’t a case yet.
More detail
Hours back a month = bills × minutes per bill × share of handling time removed ÷ 60.
Those hours at your hourly cost, a year = hours back × 12 × hourly cost. This is capacity, not cash.
Problems stopped a year = bills × 12 × share with a problem × share that get paid today × share the guards stop.
Money kept a year = problems stopped × average bill × the share of a bill a paid problem costs. This is cash.
Cash kept after running costs, a year = money kept − (running costs and support a month × 12).
Switch between Cautious and Typical in the calculator to see how much rides on the assumptions.
What it costs to run
A saving means little without the cost beside it. The calculator takes one more figure: what the workflow costs each month to run. That is the workflow software, AI model use and any support you choose to pay for. They are your own quotes, so get them in writing before you decide. The calculator starts at A$400 a month, the sample in the cost-to-own calculator, not a quote.
Keep the two kinds of saving apart. Hours back are time. They become dollars only when they replace overtime, a contractor or a hire. Money kept from duplicates and price creep is cash, and the running costs come off that number. For what a build costs to own over a full year, see what automation costs, what it saves and who owns it.
Where the money leaks today
Exhibit 4
Five problems come up again and again, and each is a control failure
01
A missing PO number
With no order number, the bill has nothing to be matched against.
02
The same bill twice
Once by email and once through a portal, so it can be paid twice.
03
A price that crept up
The price on the bill has risen since the order was placed.
04
An approver on leave
The bill waits for one person until they are back.
05
Goods that never arrived
The bill is for goods the business never received.
Illustrative figures, not client data.
Exhibit 5 · The workflow
From supplier bill to an approved draft
What gets caught: A price change is caught at step 4, ‘Match to the purchase order’.
1 of 7 · The order2 of 7 · The bill3 of 7 · Claude reads4 of 7 · Rules match5 of 7 · The mistake6 of 7 · A person decides7 of 7 · The outcome
Claude reads
Rules check
A person decides
You sent a purchase order.
PO-1182 to a building supplier: pine lengths and joist hangers, at the prices you agreed.
Then the supplier’s bill arrives.
INV-40817, by email, against PO-1182. It looks routine.
PDFPO-1182.pdf
Purchase orderPO-1182
To Building supplier
Pine lengthsA$1,104.0060 × A$18.40
Joist hangersA$523.2012 boxes × A$43.60
Subtotal
A$1,627.20
GST
A$162.72
Total incl. GST
A$1,789.92
PDFINV-40817.pdf
Tax invoiceINV-40817
From Building supplier · Your order PO-1182
Pine lengthsA$1,104.0060 × A$18.40
Joist hangersA$586.8012 boxes × A$48.90
Subtotal
A$1,690.80
GST
A$169.08
Total incl. GST
A$1,859.88
Claude (Anthropic’s AI model) reads both.
Claude turns both into the same fields. It doesn’t decide anything.
Plain rules match them, line by line.
A duplicate check, then the order: price, quantity, goods received.
Read by ClaudeOrdered · PO-1182.pdf
Read by ClaudeBilled · INV-40817.pdf
SupplierOrdered: Building supplier
✓
SupplierBilled: Building supplier. Matches
PO numberOrdered: PO-1182
✓
PO numberBilled: PO-1182. Matches
Line 1 · Pine lengthsOrdered: 60 × A$18.40 each
✓
Line 1 · Pine lengthsBilled: 60 × A$18.40 each. Matches
Line 2 · Joist hangersOrdered: 12 boxes × A$43.60
✕
Line 2 · Joist hangersBilled: 12 boxes × A$48.90. Doesn’t match
Total incl. GSTOrdered: A$1,789.92
✕
Total incl. GSTBilled: A$1,859.88. Doesn’t match
✓Not a duplicate
✓Quantities as ordered
✓Goods received
✕Hangers 12% over PO-1182
The mistake, in dollars.
Joist hangers are billed above the price on your order.
Line 2 · 12 boxes of joist hangers
Ordered on PO-1182A$43.60a box
+12%
Billed on INV-40817A$48.90a box
Over per box
A$5.30
× 12 boxes
A$63.60
GST
A$6.36
More to pay, incl. GST
A$69.96
Bill total A$1,859.88 against the order’s A$1,789.92.
It waits for a person.
Nothing goes into Xero until a person decides. Here, that’s you.
AL
Accounts leadMessage from the bill check
Held. Not in Xero.
Needs your decision
Bill INV-40817 is A$69.96 over PO-1182 on joist hangers. Approve, query the supplier or reject?
You decide: pick one to see what happens, or the run goes with “Query the supplier”.
Caught before it reached Xero.
Claude (Anthropic’s AI model) reads. Rules check. A person decides.
Approved at A$1,859.88A$69.96 more than the order, approved on purpose, not by accident.
A draft bill in Xero, and a note to #accounts naming who approved it.
XeroDraftSample
BillINV-40817
Building supplier · ref PO-1182 · for the pay run
Pine lengths60 × A$18.40A$1,104.00
Joist hangers12 boxes × A$48.90A$586.80A$5.30 a box over PO-1182, accepted
GST
A$169.08
Total incl. GST
A$1,859.88
Approved by the accounts lead
Slack #accountsSample
C
ClaudeApp9:42 am
INV-40817 from Building supplier approved at A$1,859.88 by the accounts lead: A$69.96 over PO-1182, new hanger price accepted. Saved in Xero as a draft bill for the pay run.
Claude read PO-1182 and INV-40817 into the same five fields.
Plain rules found no duplicate, then the hangers at A$48.90 a box, not the A$43.60 on the order.
The accounts lead accepted the new price, so an A$1,859.88 draft bill was saved in Xero for the pay run, with the reason on file.
When every line matches PO-1182, the accounts lead approves it and an A$1,789.92 draft bill is saved in Xero for the pay run.
Held. Not in Xero, not paid.A$69.96 more than the order, stopped before it reached Xero.
Claude’s query to the supplier, with both documents side by side.
EmailSentSample
From
Accounts lead
To
Building supplier, accounts
Subject
INV-40817: joist hangers above PO-1182
Hi, thanks for INV-40817. Line 2, 12 boxes of joist hangers, is billed at A$48.90 a box. Our order PO-1182 has them at A$43.60.
That is A$63.60 more, A$69.96 incl. GST: A$1,859.88 billed against A$1,789.92 ordered.
Could you send a credit note for A$69.96, or a corrected bill at A$1,789.92?
PO-1182.pdf
INV-40817.pdf
Drafted by ClaudeSent by the accounts lead
Claude read PO-1182 and INV-40817 into the same five fields.
Plain rules found no duplicate, then the hangers at A$48.90 a box, not the A$43.60 on the order.
The accounts lead queried the supplier, with both documents side by side. The bill waits for a credit note or a corrected bill at A$1,789.92.
When every line matches PO-1182, the accounts lead approves it and an A$1,789.92 draft bill is saved in Xero for the pay run.
Rejected. Not paid.A$69.96 more than the order, sent back before it reached Xero.
The bill, stamped and sent back to the supplier with the reason.
Returned to Building supplierSample
Tax invoiceINV-40817
From Building supplier · Your order PO-1182
Pine lengths60 × A$18.40A$1,104.00
Joist hangers12 boxes × A$48.90A$586.80PO-1182: A$43.60 a box
Total incl. GST
A$1,859.88
Rejected
Reason: joist hangers at A$48.90 a box, where PO-1182 says A$43.60. Please reissue at A$1,789.92.
Reason drafted by ClaudeRejected by the accounts lead
Claude read PO-1182 and INV-40817 into the same five fields.
Plain rules found no duplicate, then the hangers at A$48.90 a box, not the A$43.60 on the order.
The accounts lead rejected the bill and sent it back: hangers at A$48.90 a box, where PO-1182 says A$43.60.
When every line matches PO-1182, the accounts lead approves it and an A$1,789.92 draft bill is saved in Xero for the pay run.
Sample data: a fictional supplier, order and figures.
ClaudeWhere Claude helps
Reads supplier, ABN, invoice number, lines, GST and totals from the PDF
Suggests the account code and job from similar past bills
Flags any field it is unsure of for a person to confirm
RulesWhat the rules check
Invoice number, supplier and amount against bills already received
Unit prices and quantities against the purchase order and goods received
Required fields, the supplier’s ABN and the approver’s delegation limit
PersonWhat a person decides
Approves bills within their authority, with the PO alongside
Resolves price differences and likely duplicates with the supplier
Releases payment as a separate step in the bank
NoWhat Claude doesn’t do
Approve or pay a bill on its own
Change a price, a coding rule or a supplier’s bank details
Delete a bill it thinks is a duplicate
Sample data. Claude reads, plain rules check, and you make the decision. Press run to watch it get caught.
A board should be able to answer three questions with evidence. Could the business pay the same bill twice? Could it pay a price nobody approved? Could one person set up a supplier, approve its bill and release the payment?
If the honest answer is ‘we rely on people noticing’, the control depends on attention. Attention fades as volume grows and when people are away.
What it does for your team
Exhibit 6
The work moves from keying bills to questioning them
Change
What your people get
Less re-keying
AI reads the bill and rules check it, so nobody types the same figures twice
Exceptions with an owner
Each exception goes to a named person with the reason beside it, not into an inbox
Better decisions
The approver sees the bill, the order and what didn’t match, side by side
Cover when people are away
A named delegate holds an absent approver’s authority for a set period
Calmer month-ends
Bills are matched as they arrive, so the close usually has less to chase
The work that remains is the work worth paying for: querying suppliers, questioning prices and spotting a pattern before it costs you.
The controls to insist on
Exhibit 7
Three controls decide whether automation makes approval stronger
01
Delegations
Limits come from a written register: who approves what, up to what amount, for which cost centre. The workflow routes each bill and records who approved it.
02
Segregation of duties
Whoever sets up a supplier doesn’t approve its bills. Whoever approves a bill doesn’t release the payment. The workflow can refuse the preparer’s approval.
03
A person decides
AI reads the bill and suggests the coding. Rules check it against the order and past bills. A person with authority approves. Payment is a separate, authorised step.
Automation should make controls stronger, not blur them. The workflow logs every exception. AI never changes a price or a supplier’s bank details. A bank-detail change is confirmed by a person, by phone, on a number you already hold.
For the board or the audit committee, the useful report is short. It lists likely duplicates held and released, bills paid above the order price, approvals outside delegation and any override, each with a name and a reason.
What to ask your team
Exhibit 8
Six questions give you a baseline before you approve any build
Ask
Where the answer goes
How many supplier bills do we process a month, and how many active minutes does each take?
The calculator
How many needed a second look last quarter, and why?
The calculator
Have we paid a bill twice or above the order price in the last year? How did we find out?
The calculator
Is the delegations register written down, and does the system follow it?
Your risk today
Who can set up a supplier, approve its bills and release a payment? Is it ever one person?
Your risk today
What happens to a bill when its approver is away?
Your risk today
Before you approve any build, ask for a baseline. The first answers go into the calculator. The rest tell you how much risk you carry today.
What to do first
Exhibit 9
One process, one baseline month, then like-for-like months
01Start with one process
Map how bills arrive, who handles each step and where they wait.
02Record a baseline month
Time to a complete record, approval wait, correction loops and open exceptions.
03Decide who runs it
Before you sign anything, decide who runs it once it is live.
04Test the awkward bills
Not just the clean one: a missing field, a likely duplicate, a disputed amount, an absent approver and the accounting system offline.
05Compare like-for-like months
If the hours back and the money kept hold up, extend the pattern to the next process.
The decision is rarely whether to automate. It is how far to go, and who owns it once it runs.
It depends on your volume, how long each bill takes today and how many need a second look. The calculator in this article estimates hours back a month, money kept a year and the running costs and support you enter, under Cautious and Typical assumptions. Treat it as a planning estimate and measure a real month before and after, because time released is not cash saved, and running costs come off the cash that is.
Does automating invoice approval weaken financial controls?
It shouldn’t, if it is designed around them. Every bill is checked against the order and past bills, approval follows the delegations register and the person who prepared a bill can’t approve it. Payment stays a separate step, and every exception is logged with a name and a reason.
Can AI approve or pay supplier bills on its own?
Not in the workflows I build. AI reads the bill and suggests coding. Rules check it against the purchase order and past bills. A person with the right authority approves, and payment stays a separate step in your bank. AI never changes a price or a supplier’s bank details.
Chartered Accountant (CA ANZ) and finance executive, based in Canberra. Practical AI and automation for SMEs, and adviser to owners, CEOs and boards on integration and finance.
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Renzo Demartini