Reference Price: The Trick to Detecting Erroneous Invoicing

Any experienced head chef has a mental map of prices. You know that sirloin is around 32-36€/kg, that fresh hake is between 14-18€/kg, that extra virgin olive oil is about 8.50€/liter in 5-liter format. When you see an invoice, that mental map acts as a filter: if something is off, an intuitive alarm goes off.

The problem is that this mental map:

Only works for the 20-30 most used products.
Only works if the reviewer is the same person who cooks.
Takes months to form when there is staff turnover.
Is difficult to transmit.
Works worse the more tired you are.

The professional solution is to convert that mental map into data. Assign each product a reference price recorded in your system, and automatically compare each invoice against it. That's exactly what restaurants that stop paying invoices blindly do.

What is the Reference Price

The reference price for a product is the expected value according to your agreement with the supplier or the market range. It is not the last price (which may be temporary) nor the lowest historical price (which may be unrealistic). It is the number you expect to pay for the next order.

There are three ways to establish it:

1. Agreed Price. If you have a formal or informal agreement with your supplier for a product at a fixed price, that is your reference.

2. Historical Average. For products without an agreed price but with recurring purchases, the moving average of the last 3-6 months serves as a reference.

3. Market Range. For sporadic or new products, the reasonable range according to other suppliers or external references.

Any of the three is valid. The important thing is that each recurring product has one.

How it's Used in Practice

Once you have the reference price, each new invoice goes through an automatic check:

For each invoice line item:
  If the invoiced price deviates more than N% from the reference price:
    Flag the line for human review.

Where N is a configurable threshold (typical: 5-10%). Below the threshold, it's assumed to be normal variation. Above it, you need to investigate.

The result: in a monthly invoice with 80 line items, the system flags 2-5 lines that need your attention. The rest pass through. The flagged ones are exactly where the money is at stake.

Typical Cases the Reference Price Detects

1. Silent Price Increase. Product X was 4.80€. This month's invoice shows it at 5.20€. An 8% increase. Without a reference price, this goes unnoticed in an invoice with many line items. With a reference price, it flags as a discrepancy and is managed before payment.

2. Grade Error. They invoice you for "1st grade" tomato at the price of "extra." Same product in a different category, different price. The reference price (tied to the exact product category) detects the mismatch.

3. Quantity↔Price Inversion. They deliver 8 boxes at 12€/box, but invoice you for 12 boxes at 8€/box. The total matches (96€) but the detail is wrong. If the reference price is 12€/box, the line with 8€ flags as anomalous.

4. Incorrect IVA. They apply 21% instead of 10% on a food product. If your reference price includes the expected IVA, the difference flags.

5. Disguised Extra Charges. A line item with the concept "Service Surcharge" at 25€ that appears where it never did before. Without history, it seems normal. With history, it's a new concept to investigate.

How to Set Reference Prices Without Working 100 Hours

The good news: if you've been digitizing invoices for some time, the reference price can be automatically generated for each recurring product. The system sees that you've bought tomatoes from the fishmonger 18 times in the last 6 months at prices between 4.70-4.95€, and proposes 4.82€ as a reference.

The bad news: if you don't have a digitized history, the first time you set reference prices is manual. Recommendation: start with the 30 products that move the most volume (they probably represent 70-80% of the total cost). With 30 well-placed references, you already have a very useful tool. The rest can be added as the months go by.

When to Review Reference Prices

The reference price is not static. It's advisable to review it:

After Renegotiations. When you agree on new prices in an annual negotiation, update your references the next day.
After Clear Seasonality. Products like fresh fish have different prices in season vs. out of season. It's worth having seasonal references (summer vs. winter).
If the Deviation Becomes Systematic. If a specific line item is flagging as a "discrepancy" month after month with the same magnitude, it's no longer a discrepancy: it's the new normal. Review the reference.
Every 6-12 Months at Minimum. Even if there are no specific triggers, a periodic review keeps the data alive.

Mistakes to Avoid

1. Overly Strict Thresholds. If you set N=2%, practically every line item will flag as a discrepancy. The system becomes noisy. It's better to start with 8-10% and lower it if the results are good.

2. Applying the Same Threshold to Everything. Commodity products (branded oil, flour, canned goods) allow for stricter thresholds (3-5%). Fresh products with natural variation (fish of the day, seasonal vegetables) allow for broader thresholds (10-15%). Differentiating reduces noise.

3. Not Acting When Flagged. If the system flags discrepancies and no one reviews them, the system is just decoration. Assign the review to a specific person with a fixed schedule (e.g., Monday mornings).

4. Sticking to the Last Price. If a supplier lowers the price one month due to a temporary promotion, don't automatically update the reference downwards. Temporary promotions are not the new normal.

Conclusion

The reference price is the simplest and most underutilized tool in hospitality purchasing management. Converting your mental map into data accessible to the system (and the team) changes the dynamic: instead of reviewing entire invoices in detail (slow, error-prone), you review only the flagged discrepancies (fast, targeted).

Modern tools can automatically generate references from your history and check each new invoice against them in real time. What used to be a weekly process is now an automatic alert when something is off.

If you want to see how Sincrio automatically detects discrepancies in your invoices, start a free trial.