Why it’s worth checking
Most invoice differences aren’t deliberate. A quote expired before the order was placed, a price was keyed in the wrong unit, a partial shipment was billed in full, or a substitute was invoiced at a different price. Each one is small on its own. Across dozens of invoices a month, they add up — and they’re far easier to fix before payment than after.
Step 1: Gather the documents
For each invoice, pull together:
- The quote you accepted
- The purchase order you sent
- The delivery record — the packing slip or delivery ticket signed on receipt
- The invoice itself
Matching the purchase order, the delivery record and the invoice is often called a three-way match. Adding the quote makes sure the price you were promised is the price on the order.
Step 2: Check the header
- Supplier, job name and job address are correct
- The purchase order number is on the invoice
- The invoice isn’t a duplicate of one you’ve already received
Step 3: Check every line
For each line, compare the invoice with the quote, purchase order and delivery record:
- Item. Is it the catalog number you ordered? If it’s a substitute, was it approved — and at what price?
- Quantity. Does the quantity billed match the quantity actually delivered? Partial shipments should be billed only for what shipped.
- Unit price. Does it match the quoted or agreed price?
- Pricing unit. Is it priced per each (E), per hundred (C) or per thousand (M) — and is that the same unit as the quote?
- Extended price. Is unit price times quantity calculated correctly?
Step 4: Check the extra charges
Look for charges that weren’t on the quote:
- Freight, delivery or fuel charges
- Small-order or handling charges
- Restocking charges
- Price adjustments on wire and cable — some quotes are subject to metal prices at the time of shipment, so check what your quote said
- Taxes applied correctly for the job location
Step 5: Check for credits you’re owed
- Returns you’ve sent back should appear as credits.
- Short or damaged deliveries reported on receipt should be credited.
- Pricing agreements for the job should be reflected in the price.
Step 6: Resolve differences quickly
- Contact the supplier in writing with the invoice number, the line, what you expected and what was billed.
- Ask for a credit memo or corrected invoice for anything billed in error.
- Follow your supplier’s terms for disputed amounts — many contractors pay the lines that match and hold only the disputed ones until they’re resolved.
- Record the outcome, so the same issue is caught faster next time.
Make it a routine
- Check before you pay, not months later.
- Decide who checks what. Many contractors check every line on large invoices and spot-check small ones.
- Reconcile monthly statements against the invoices you’ve checked and the credits you’re owed.
- Watch for patterns. The same error from the same supplier is worth a conversation.
Common mistakes
- Checking the invoice total instead of each line
- Comparing prices without checking the pricing unit
- Paying for a full shipment when only part was delivered
- Missing freight or adjustment charges that weren’t on the quote
- Forgetting to chase credits for returns
- Resolving a dispute by phone and not recording it