How to Audit a Co-Packer Invoice for Hidden Costs

Your co-packer relationship is the most critical partnership in your supply chain. But when their monthly invoice arrives, many founders simply glance at the total and pay it. This is a massive mistake. Co-packer invoices are notoriously complex, and failing to audit them against your production records can cost you tens of thousands of dollars in hidden fees and undocumented yield loss.

The Anatomy of a Tolling Invoice

If you operate under a tolling agreement (where you supply the ingredients and the co-packer provides the labor and equipment), the invoice should reflect the specific services rendered. A standard invoice will include:

• Tolling Fee: The base charge per unit, per case, or per hour of production.
• Setup/Changeover Fees: Flat fees charged to clean and sanitize the line between different SKUs (especially critical for allergen changeovers).
• Accessorial Charges: Fees for services outside the core production, such as palletizing, shrink wrapping, storing your raw materials, or handling inbound freight.

Where to Look for Margin Leaks

When auditing the invoice, you must cross-reference the charges against the actual Batch Production Records (BPRs) for that month. Look for these three common discrepancies:

1. Billed Units vs. Received Units

The co-packer will bill you for the number of units they produced. You must verify this number against the number of units your 3PL actually received. If the co-packer billed you for 10,000 cases, but the 3PL only received 9,800 cases, where are the missing 200 cases? You should not pay tolling fees on units that never made it to your warehouse.

2. The Yield Loss Subsidy

This is the most expensive hidden cost in co-packing. Suppose your BOM states that 1,000 lbs of ingredients should yield 10,000 units. The co-packer consumes 1,000 lbs of your ingredients but only produces 9,000 units (a 10% yield loss). They will bill you for the 9,000 units produced.

If you don't audit the ingredient consumption, you might think the run was fine because the tolling fee matched the output. But you just lost 10% of your expensive raw materials to scrap. You must track actual yield against expected yield on every run, and enforce the shrinkage allowance in your contract.

3. Unapproved Accessorial Fees

Look closely at the line items for storage and handling. Did they charge you a "pallet in/out" fee for ingredients you sourced? Did they charge you for storing your packaging materials longer than 30 days? Ensure every accessorial fee matches the pricing schedule in your master manufacturing agreement.

Automating the Audit

Auditing invoices manually requires cross-referencing PDFs and spreadsheets. Operations platforms like Guidance automate this by linking the original Work Order, the recorded ingredient consumption, and the finished goods receipt. When the invoice arrives, you can instantly see if the billed quantities and yield loss align with reality.