If someone in your office opens every supplier bill, types it into Xero or QuickBooks, chases a manager by email to approve it, then files the PDF, you can automate most of that work this month with tools you probably already pay for. This guide shows how to automate supplier invoice processing in a 10 to 50 person engineering, technical or SaaS business: what to switch on, where AI helps and where it doesn’t, a fully worked £ example, and a checklist you can start this week.
Most guides on this topic are written by software vendors comparing their own product with a rival’s. We’re not selling software. The aim here is to help you decide whether it’s worth doing, what it’s worth in £, and how to do it without creating new problems.
Where the time and money go when bills are handled by hand
Supplier invoices look like a small admin job. In a firm buying from dozens of subcontractors, hire companies, software vendors and parts suppliers, they add up to four kinds of cost:
- Keying time. Opening the email, downloading the PDF, typing supplier, date, amount, VAT and description, picking the account code, attaching the file.
- Approval chasing. “Can you OK this?” emails to project managers who are on site, followed by reminders, followed by the bill sitting in someone’s inbox for three weeks.
- Missed recharges. Costs that should be passed on to a customer (equipment hire, a specialist subcontractor, extra travel) get coded to general overheads and never reach the customer’s invoice. This is usually the biggest £ figure and the one nobody measures.
- Errors. The same bill entered twice, a wrong VAT figure, a supplier’s changed bank details accepted without a check.
Automation helps with all four, but only if you design it around them. Simply making data entry faster fixes the first and leaves the expensive third one untouched.
A worked example: what it’s worth in £
Example Fire Protection Services Ltd is a made-up technical services firm with 30 staff. Every figure below is an assumption for illustration. Swap in your own.
It receives about 260 supplier invoices a month. Its bookkeeper spends around 8 minutes on each one by hand, and her time costs the business £20 an hour including employer costs. The operations manager spends about 2 hours a week chasing approvals, and his time costs £40 an hour. Looking back over a year of jobs, the owner finds 12 supplier bills, averaging £650, that should have been recharged to customers but weren’t.
Before automation
- Keying: 260 × 8 minutes = 2,080 minutes = 34.7 hours a month. 34.7 × £20 × 12 = £8,320 a year.
- Approval chasing: 2 hours × 46 working weeks = 92 hours. 92 × £40 = £3,680 a year.
- Missed recharges: 12 × £650 = £7,800 a year of income never billed.
After automation (bills arrive by email, the software reads them, a person checks each one, approval happens in the app, and a job code is required before approval):
- Keying becomes checking: 260 × 2 minutes = 520 minutes = 8.7 hours a month. 8.7 × £20 × 12 = £2,080 a year. Saving: £8,320 − £2,080 = £6,240.
- Approval chasing drops to half an hour a week: 1.5 hours saved × 46 weeks × £40 = £2,760.
- Requiring a job code at approval catches 10 of the 12 recharges: 10 × £650 = £6,500 more billed.
Total: £6,240 + £2,760 + £6,500 = £15,500 a year. Take off an assumed £60 a month (£720 a year) for an extra capture or approval tool, and the net figure is £14,780. In hours, the firm gets back about 312 hours of bookkeeping and 69 hours of a manager’s time, roughly ten working weeks in all.
Two things stand out. First, the recharges are worth more than the manager’s time saved and nearly as much as the keying saved, and they come from a process rule (job code required), not from AI. Second, the hours saved are only worth money if they go somewhere useful. If the bookkeeper spends them on same-day sales invoicing and chasing customers, the cash benefit is bigger than the table shows. If they disappear into the week, it isn’t.
What it takes to automate supplier invoice processing
A working set-up has five stages. Each one can be done with mainstream tools.
1. One way in
Every bill should arrive in one place. Both main packages give you a dedicated email address for this. Xero lets you forward a supplier’s bill to your Xero email address, photograph paper receipts in its app or drag and drop files, and its data capture page says this is available on all its small business plans. QuickBooks Online UK lets you set up a forwarding address (under Receipts, then Forward from email) that accepts PDF and image files. Then ask suppliers to send invoices to a shared address such as accounts@ and set that inbox to forward automatically.
2. Reading the bill
This is where AI does real work. The software reads the supplier name, date, invoice number, net amount, VAT and total, and, depending on the tool, suggests a supplier and account code. QuickBooks describes it as extracting the information and creating a transaction for you to review. Specialist capture tools such as Dext, Hubdoc and AutoEntry, all listed in the Xero app store, offer more settings for higher volumes. Whether you need one depends on volume and how messy your bills are. Test the built-in option first.
3. A human check
Keep a person in the loop. AI extraction is good on clean PDFs and weaker on scanned delivery notes, multi-page subcontractor valuations and bills with credit lines. The check should take a minute or two, not eight: confirm the total matches, the VAT looks right and the supplier is the right one. Your accountant can tell you what a valid VAT invoice needs to show before you reclaim the VAT on it.
4. Approval with a job code
Approval should happen in the system, on a phone, without an email thread. Set simple rules: bills under a threshold (say £500) approved by the bookkeeper against a purchase order, bills above it by the project manager, anything over a higher limit by a director. Make the job or project code compulsory, with a yes/no field for “recharge to customer”. That one field is what found £6,500 in the example. If your accounting package doesn’t do multi-step approval on your plan, approval apps (ApprovalMax is one listed for Xero) or a Power Automate or Zapier flow can route bills to the right person.
5. Payment and filing
Approved bills go into a weekly payment run on a fixed day, so suppliers know when to expect money and nobody pays ad hoc from the banking app. The PDF stays attached to the bill in your accounting software. Limited companies must keep accounting records, including what the company spends, for 6 years from the end of the financial year they relate to, so check with your accountant that your digital set-up meets that before you shred any paper.
Where AI helps, and where it doesn’t
AI is good at reading documents, suggesting codes from history and spotting likely duplicates. A general assistant such as ChatGPT, Claude or Microsoft Copilot can also help with the messy edge cases: summarising a 12-page subcontractor valuation, or comparing a bill against the purchase order and listing the differences.
It is not good at judgement it hasn’t been given. It doesn’t know a hire charge belongs to the Smith Road job unless someone tells it, and it can’t tell whether a supplier’s “new bank details” email is genuine. Those two decisions stay with people. Before you paste supplier documents into any general AI tool, agree which tools are allowed and check where they store data. Supplier invoices from sole traders can include personal details.
We’ve seen the wider effect when a small organisation automates its routine finance work: for a small UK charity, admin time fell by about 85% after we automated its accounting and reporting. Supplier bills are usually the easiest place to start, because the volume is high and the rules are simple.
Checklist: what to do this week
- Count. How many supplier bills arrived last month? Pull the number from your accounting software.
- Time ten. Ask whoever enters bills to time the next ten from opening the email to filing. Multiply the average by your monthly count.
- Find the recharges. Take the last 50 bills coded to general overheads and ask the project managers which ones belonged to a customer job. Multiply by 12 to get a year.
- Switch on the inbox. Set up the Xero or QuickBooks bill email address and forward ten bills to it. Compare what it reads with what’s on the PDF.
- Write three rules. Who approves what value, which field is compulsory (job code), and the payment run day.
- Tell suppliers. Send one email giving the address bills should go to and asking for your purchase order number on every invoice.
- Set the bank-details rule. Any change to a supplier’s bank details is confirmed by phone, using a number you already hold, before the change is made.
Run the new set-up alongside the old one for a month. At the end, re-time ten bills and count the recharges caught. That gives you the before-and-after figure, rather than a vendor’s estimate.
Common mistakes
- Buying a tool before counting. A firm with 60 bills a month and one with 600 need different set-ups. Count first.
- Letting AI post without review. Auto-publishing bills saves a minute each and costs hours when a wrong VAT figure reaches a VAT return. Keep the check.
- Automating the mess. If bills currently go to five different inboxes and nobody knows who approves what, automation makes the confusion faster. Fix the rules first.
- Too many approval steps. Three approvers on a £40 bill means it never gets paid. Use value thresholds.
- No job code. This is the step that turns admin savings into extra income. Without it, recharges keep slipping.
- Dropping supplier statement checks. Reconcile your biggest suppliers’ statements monthly. It catches bills that never arrived and bills entered twice.
How this fits with the rest of your finance admin
Supplier bills are one end of the cash cycle. The other end is getting your own invoices out and paid. If you’ve automated bills, the natural next steps are automating invoice reminders and checking job margins, which is far easier once every supplier cost carries a job code. Our AI and automation work starts the same way as this article: time the manual tasks, put a £ value on each, and automate the one that pays back fastest. You can see the steps on how it works and the packages on our profit improvement consulting page.
Find out what manual admin is costing you
Our free leak calculator takes about two minutes and gives a rough £ figure for cash and profit leaks in your business. If you’d like to talk through where automation would pay back first, book a free 30-minute call.
