The Supplier Invoice That Crept Up and Nobody Noticed (And How to Check Your Prices in Twenty Minutes a Month)

Meta description: Supplier price creep can quietly eat your margin. Here is a simple twenty-minute monthly check for London small business owners.

Your accountant asks why food cost has moved.

You stare at the figures.

Nothing dramatic happened. You have not changed the menu. You have not ordered anything outrageous. You have not suddenly started throwing chicken breasts into the bin for fun.

Then you check the invoices.

The same box of ingredients costs more than it did three months ago.

The same salon supplies cost more.

The same office consumables cost more.

Nobody called you. Nobody waved a little flag. The total invoice still looked roughly familiar because you happened to buy fewer items that week.

That is supplier price creep.

It is quiet, ordinary and very good at stealing money while you are busy serving customers, managing staff and trying to remember whether you have paid the electricity bill.

Supplier price creep hides inside the total

Invoice totals are not enough.

A total can go up because you bought more. It can stay the same because you bought less. It can even fall while the individual items you rely on are becoming more expensive.

You need to look at the unit price.

That means the price of one bottle, one kilogram, one case, one box, one treatment product or one pack. Whatever makes sense for the item you buy.

An illustrative scenario from a London cafe

Illustrative scenario only.

Three months ago, a cafe paid £18 for a case of oat milk.

Last month, the owner paid £20.50.

That increase may not look enormous on one invoice. But if the cafe buys several cases every week, it starts to affect the cost of every latte, every flat white and every iced coffee.

The owner only notices when the accountant asks why food cost has moved, or when a customer complains about a menu price increase.

By then, the price change has been sitting there quietly doing its little financial horror show.

You do not need a complicated system to catch it.

You need twenty minutes, once a month, and a rule you actually follow.

The twenty-minute supplier price creep check

Here is the full method.

No expensive software required. No spreadsheet degree required. No need to become the sort of person who enjoys colour-coding cells.

1. Pick the ten items that move your money

Choose ten line items that matter most to your business.

For a restaurant or pub, that might be:

• Cooking oil
• Chicken
• Beef
• Coffee
• Oat milk
• Eggs
• Flour
• Fresh produce
• Takeaway packaging
• Cleaning products

For a nail salon, it could be:

• Gel polish
• Acetone
• Gloves
• Files
• Cotton pads
• Disinfectant
• Towels
• Nail tips
• Cuticle oil
• Disposable masks

For an accountant or consultant, it may be:

• Software subscriptions
• Printing
• Postage
• Stationery
• Client folders
• Business cards
• Meeting room hire
• Phone services
• Cloud storage
• Outsourced admin support

Do not try to track everything on day one.

Pick the five or six things you buy every single week, then add the other items that have a noticeable effect on your costs. Ten is enough to start.

2. Keep every delivery note and invoice in one place

For one month, keep the documents together.

That could be:

• A paper folder behind the till
• A folder in your email
• A folder in Google Drive
• A folder of photos on your phone
• A simple accounting system

The best system is the one you will keep using.

If your team receives deliveries, tell them exactly where the paperwork goes. Do not rely on someone saying, “I think I left it somewhere near the office.”

That sentence has swallowed many a useful document.

3. Compare last month’s prices with this month’s prices

Once a month, sit down for twenty minutes.

Put last month’s price list or invoices beside this month’s invoices.

Write down the unit price for each of your ten items.

Not the invoice total.

The unit price.

If you bought 12 bottles for £48, the unit price is £4 per bottle. If you bought one case for £36, record the price of that case and the pack size too.

Pack sizes matter. A supplier can make an item look cheaper while quietly reducing the quantity inside the box.

The question is simple:

What does one comparable unit cost now, compared with last month?

This is why totals hide price rises. You may have bought six cases instead of eight. The total fell, but the price per case went up.

4. Set a five per cent rule

If any tracked item has gone up by 5 per cent or more, call the supplier.

You can calculate it like this:

New unit price minus old unit price, divided by old unit price, multiplied by 100.

For example, if something was £10 and is now £10.50, it has gone up by 5 per cent.

You do not need to start a fight.

Ask a plain question:

“Hi, I have noticed this item has gone up by 5 per cent or more. Has something changed on your side, and can we look at the price again?”

That is it.

Perhaps there is a genuine cost change. Perhaps a promotion ended. Perhaps the pack size changed. Perhaps the invoice is wrong. Perhaps they can offer another product or review your pricing.

You will not know until you ask.

5. Ask for the price in writing

After the call, ask the supplier to confirm the price by email.

Keep that email with your invoices.

You now have a simple record of:

• What the item cost before
• What it costs now
• What explanation you were given
• What price was agreed
• When you should check it again

This is basic supervision.

You are not being difficult. You are checking the numbers that pay your bills.

This is a management problem, not a tech problem

Supplier price creep is the same as a member of staff quietly doing something differently every week and nobody checking the work.

Not because they are necessarily doing anything wrong.

Because the process has no clear owner, no clear standard and no regular review.

You would not give a team member a job with no instructions, never look at the results and then act shocked six months later.

The same applies to your numbers.

You need to know:

• What you are checking
• How often you are checking it
• What counts as a problem
• Who follows up
• Where the record is kept

That is also how you should think about AI.

Where AI helps with supplier price creep

AI can read invoices and delivery notes, extract the item names and prices, and keep a running list.

It can compare this month with last month.

It can flag an item that moved by 5 per cent or more.

That could reduce the twenty-minute monthly review to a much quicker check, especially if you receive a lot of invoices.

But let us be honest about the limits.

AI can get confused by:

• Handwritten delivery notes
• Blurry phone photos
• Odd abbreviations
• Different names for the same product
• Changed pack sizes
• Discounts shown in unfamiliar places
• Invoices with confusing layouts

It cannot phone the supplier for you.

It cannot negotiate properly on your behalf.

It cannot decide whether a price change is reasonable for your business without you checking the context.

A human still needs to review the flagged items.

And if a spreadsheet plus a diary reminder is what you will actually keep up with, use that. There is no prize for making a simple job complicated.

AI needs a job description and supervision too

At Phare HR, we use the same workforce management thinking with AI as we do with people.

An AI employee needs a clear job description.

For example:

“Review supplier invoices every month. Track the unit price of these ten items. Compare each price with the previous month. Flag increases of 5 per cent or more. Do not contact suppliers. Ask a human to check unclear documents.”

That is much more useful than telling an AI tool to “keep an eye on costs”.

Who checks its work? You do, or someone you nominate.

What happens when it is unsure? It flags the item instead of guessing.

That is the practical thinking behind Amplified Impact. You use tools to extend your capacity, while keeping human judgement where it matters.

Through Back of House by Phare HR, the aim is simple: AI staff, set up and managed.

No promise that AI will run your business while you sleep. No pretending a robot can replace your supplier relationship. Just a sensible member of your admin team doing a defined job, with somebody checking the work.

Start with twenty minutes and protect your soft life

You do not need to spend your Sunday evening staring at every invoice your business has ever received.

Start with ten important items.

Set a monthly calendar reminder.

Keep the paperwork together.

Compare the unit prices.

Call when something moves by 5 per cent or more.

That small routine can help you spot changes before they become a customer-facing price rise or an awkward conversation with your accountant.

And if you want to learn where AI genuinely fits into this kind of admin, the free class You didn't fail at AI. You hired it badly. is on Tuesday 29 September 2026, 17:00 to 18:30 BST, which is 12pm to 1:30pm ET / Eastern. You can register here.

Want to see how Back of House by Phare HR could support your admin? Visit phareboh.com.

You've got this! XO, Amber.