Business cost audits

Invoice Auditing Services: What They Find, What They Cost, and the Audit Most Businesses Skip

Invoice auditing services check the bills your business pays against what you actually agreed to and actually received. They are best known in freight and shipping, where carrier billing is complicated enough to hide real money. Here is how they work and what they charge, and then the one bill most businesses never audit at all.

Written by Robert Day, Founder and Managing Partner of weAudit.com, previously an executive at Fifth Third Processing Solutions, later Vantiv and Worldpay, now part of Global Payments, the world’s largest card processor. Published October 2026.

What an invoice audit does

It compares every invoice with the contract, the rates you negotiated and the record of what was actually delivered, and flags anything that does not match: duplicates, wrong rates, charges for services you never received.

Done before payment, it stops errors leaving your account. Done after, it recovers money already paid.

The bill nobody audits

Card processing fees are never invoiced and never approved. They are simply taken from your bank account. Here is why that makes them the fastest audit most businesses can run.

Figures in brief

3% to 7%: how much of total freight spend freight audit firms commonly estimate is lost to billing errors.
Two kinds of audit: pre-payment, which stops errors before money leaves, and post-payment, which recovers it afterward.
Contingency: how many outsourced freight auditors are paid, keeping a share of what they recover or save.
About 99 percent: the share of weAudit’s card processing audits that find savings.

What invoice auditing services check

An invoice audit is only as good as the documents it compares against. A good service matches each bill to three things: the contract or rate agreement, the record of what was actually delivered, and what has already been paid. The most common areas are:

Type of audit	What it compares	Typical findings
Freight (LTL and truckload)	Carrier invoices against contract tariffs and bills of lading	Rate variances, reclassification and reweigh charges, unauthorized accessorials, duplicate bills
Parcel (small package)	Ground and express invoices against contracted discounts and delivery scans	Dimensional weight errors, residential and address-correction surcharges, missed late-delivery refunds
Accounts payable recovery	Payments made against vendor contracts and credits due	Duplicate payments, missed discounts and rebates, unapplied credits
Telecom and utilities	Service bills against contracts and inventory	Billing for closed lines or services, wrong rate plans

The freight and parcel errors audits catch most

Duplicate invoices. The same shipment billed twice, often weeks apart and under a slightly different invoice number.
Rates above contract. The negotiated discount fails to apply and the invoice is billed at a higher rate.
Accessorials that never happened. Liftgate, inside delivery, residential or detention charges that do not match the delivery record.
Weight and dimension errors. Reweigh charges and dimensional weight calculations that bill for more than shipped.
Fuel surcharge errors. Surcharges calculated from the wrong index period or on the wrong weight.
Missed service refunds. Late deliveries on guaranteed services where a refund was due and never claimed.

How invoice auditing services charge

There are three common models. Outsourced audit firms often work on contingency and keep a share of what they recover or save. Others charge a flat or per-invoice fee. And some sell software your own team runs. Before signing, ask:

What share, and for how long?

A contingency on refunds is different from a share of every future saving for years.

Pre-payment, post-payment, or both?

Stopping errors before payment is cleaner than chasing refunds afterward.

Who owns the data?

Your invoice history is valuable. Make sure you keep it if you leave.

The audit most businesses skip: card processing

A business that audits its freight invoices is already doing something most do not. But there is a bill that often gets less scrutiny than any of them, and it is the one that is easiest to audit: what you pay to accept credit cards.

Three things make card processing unusually fertile ground for savings.

It is a non-regulated industry

There is no rate filing, no required statement format and no rule about what a processor may call a fee. The people who sell processing need no license, exam or education. Processors can quote one rate, inflate the network fees underneath it, add fees with official-sounding names, and change their pricing after you sign, all within the terms of a standard merchant agreement.

Nobody approves the bill

A freight invoice goes through accounts payable and someone approves it before it is paid. Processing fees never do. Your processor has unlimited and unvetted access to your business bank account, and takes its fees directly, often as a single debit with a cryptic label. Most businesses never see an itemized bill they could question. Read why your bank account is the keys to the kingdom.

The savings are fast

A freight audit can mean months of matching shipments to invoices. A card processing audit starts from a few monthly statements. weAudit’s audits find savings in about 99 percent of cases.

The pattern is the same as freight. Wrong rates, charges for services you never received, and duplicates nobody caught. The difference is that card processing fees are taken before anyone looks, in an industry with no regulator watching.

See what processing costs you, in seconds

Grab a recent merchant statement and try one of our free calculators. Each one takes a few seconds and gives you a quick idea of how much card processing is costing your business:

Credit card processing fee calculator: find your effective rate from your volume and total fees.
Savings calculator: estimate what a properly priced account could save.
Stripe, Square and PayPal fee calculators, if you use one of those platforms.

All of them are on our fee calculators page.

Then get the real answer. A calculator gives you an estimate. A full line-by-line audit tells you exactly what you are paying, what should be lower, and what should not be there at all. Your first weAudit audit is free, with no strings attached.

Common questions

What do invoice auditing services do?

They check the invoices your business receives against what you actually agreed to pay and what was actually delivered: contract rates, delivery records, purchase orders and payment history. The most common type is freight and parcel auditing, but the same idea applies to telecom, utilities and accounts payable.

What does a freight invoice audit look for?

Duplicate invoices, rates billed above your contract, accessorial charges for services that never happened, dimensional weight and reweigh errors, fuel surcharges calculated from the wrong index or weight, and missed refunds on late guaranteed deliveries.

How much do invoice auditing services cost?

Many outsourced freight audit firms work on contingency, keeping a share of what they recover or save. Others charge a flat or per-invoice fee, or sell software you run yourself. Ask what share they keep, for how long, and whether it applies to future savings as well as refunds.

What is the difference between a pre-payment and a post-payment audit?

A pre-payment audit checks each invoice before it is paid, so errors never leave your account. A post-payment audit reviews invoices already paid and tries to recover overcharges afterward. Many businesses use both.

Should credit card processing be audited too?

Yes, and it is often the faster win. Processing fees are taken straight from your bank account without an invoice anyone approves, card processing is a non-regulated industry, and fees can change after you sign. weAudit audits find savings in about 99 percent of cases.

How can I estimate what card processing costs my business?

Use a fee calculator with a recent statement: enter your monthly card volume and total fees and it shows your effective rate in seconds. For a line-by-line answer, weAudit’s first audit is free with no strings attached.

Get a free line-by-line audit of your card processing.

Send us a recent statement. We check every fee, every rate and how your account is set up, and show you what you should be paying. It costs nothing, there are no strings attached, and if there is nothing to find, you will know that too.

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About the figures: the 3% to 7% range is a common estimate published by freight audit firms in 2025 and 2026 and varies widely by shipper and mode. Freight and parcel error types reflect those firms’ published guidance. The share of audits that find savings is weAudit’s own figure. weAudit audits card processing; it does not provide freight or parcel audit services.