Vendor Overbilling: How to Detect It and How to Dispute It
Most vendor overbilling is not fraud. It is a rate card that drifted, a discount that expired quietly, and an invoice nobody had time to read line by line.
Vendor overbilling has a reputation problem. The word suggests deliberate deception, and that framing makes finance teams reluctant to raise it, because accusing a supplier of fraud is a relationship decision, not an accounting one. In practice, almost all overbilling is drift: a rate that was negotiated in one system and billed from another, a promotional discount with an end date nobody tracked, a service tier that was downgraded in a support ticket and never in billing.
Reframing it as reconciliation rather than accusation makes it much easier to act on, and it happens to be accurate.
The five checks
1. Rate card versus invoice
Take the contracted unit rate and multiply by the quantity on the invoice. If the line total does not match, you have a finding. This is trivial arithmetic and it is skipped constantly, because doing it requires having the contract open, and the contract is usually a PDF in someone's email.
2. Discount persistence
Promotional pricing has an end date. Contracted pricing does not. Check whether every discount you believe you have is still being applied, and check the reverse: whether a discount that should have ended is still running in your favour, because vendors do eventually notice those and backbill.
3. Tier thresholds
If your contract prices at a lower rate above a volume threshold, verify the rate changed on the invoice covering the period you crossed it. Tier changes are applied manually far more often than anyone expects.
4. Provisioned versus billed
Compare the line items on the invoice to the services you are actually consuming. Seats for departed employees, environments that were decommissioned, and add-ons from a trial that was never converted are the three that recur.
5. Escalation clauses
Annual uplifts are usually capped, often tied to an index, and frequently applied early or above the cap. Check the effective date of every price increase against what the contract permits.
The dispute sequence
Order matters more than tone here. The goal is a cash refund, and the default outcome of a badly sequenced dispute is a credit against future invoices, which is worth materially less if you are planning to reduce spend with that vendor.
- Quantify the full exposure before making contact, including every prior period affected. Opening with one month invites a one-month remedy.
- Attach the contract clause and the invoice line side by side. A dispute that requires the vendor to go find your contract will take three weeks longer.
- Ask for a specific remedy in the first message: a refund to the original payment method, by a named date.
- Send it to accounts receivable or billing operations, with your account manager copied rather than addressed.
- If a credit is offered instead of a refund, ask what happens to that credit if you do not renew. The answer is usually the argument for cash.
- Escalate on a schedule, not on frustration. A calendared follow-up at seven and fourteen days recovers more than a strongly worded email at day thirty.
Making it continuous
Every check above is a comparison between a contract and a ledger. The reason they get skipped is not difficulty, it is that nobody owns doing them every month for every vendor. Leaki runs these comparisons automatically against your connected accounting system, ranks findings by recoverable value, and drafts the dispute letter with the evidence already attached, so the work left for a human is the decision rather than the assembly.