TSA Renegotiation
Invoice errors stacking up month after month? Reset the terms.
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TSA charge validation is the monthly discipline that decides whether a buyer pays the right number or the seller's number. Each line on the invoice should be tested against the service catalog, the agreed rate, the volume actually consumed, and the agreed cost basis, and any line that fails is logged before it is paid. Treat it as the operating layer beneath disciplined TSA cost reduction, because a charge never tested is a charge the seller has effectively set.
A seller invoice is not a statement of what the buyer owes. It is the seller's claim of what the buyer owes, produced by billing systems that were built to allocate cost inside one enterprise, not to honor a contract with an outside party. Those systems do not know the service catalog, do not track the agreed rate, and have no concept of a service that has exited. They produce numbers, and the numbers arrive looking authoritative.
A buyer that pays the invoice as presented has handed the seller the power to set the price every month. The agreement may be precise, but precision in the contract does nothing if the invoice is never held against it. The gap between what was negotiated and what is billed is where money quietly leaves the carved out business.
Validation closes that gap. It is not an accusation against the seller and it does not assume bad faith. It is the routine confirmation that the charge matches the agreement, line by line, before payment leaves the building. The discipline is simple. The cost of skipping it is not.
Each line on the invoice should survive five tests before it is approved. Run them in order, because a line that fails the first test does not need the others, and a single failure is enough to hold the charge.
A line that passes all five is approved and paid. A line that fails any test is held, logged, and routed to governance with the specific reason attached. The point is not to argue every charge. It is to pay only the charges that are genuinely owed.
The same errors appear across carve-outs because they come from the same source. The most common is the charge for a service that exited weeks ago. The buyer stood the function up internally, told the seller, and the charge kept arriving because nobody switched it off in the billing system. This is the easiest money to recover and the easiest to miss.
Next is volume that does not match consumption. A per seat or per transaction charge bills for a headcount or a usage level the business no longer carries. The seller is billing from a stale figure, and only the buyer holds the current number. Then there is mark-up creep, where the percentage applied has drifted above the agreed rate, or a fair sounding mark-up sits on an inflated allocated base.
Finally there is the new charge that simply appears, a service nobody agreed to, bundled into the run rate. Each of these is recoverable, but only if the buyer is testing every line. None of them announce themselves. They hide in a long invoice that looks, at a glance, exactly like last month's.
The most common mistake in validation is checking this month's invoice against last month's invoice. That only confirms the charge has not changed. It does nothing to confirm the charge was ever correct. If an error entered the run rate in month one, comparing each month to the previous one carries that error forward untouched for the life of the agreement.
Validation should run against the cost model the buyer built, not against prior invoices. The model holds the expected charge for each service at the agreed rate and volume, so every line can be tested against an independent baseline rather than a number the seller produced. When the invoice and the model diverge, the model is the reference point and the burden sits with the seller to explain the line.
This is why a usable cost model is the precondition for validation. Building it is covered in detail in our guide to constructing a TSA cost model, and the variance work that follows is the subject of budget variance tracking. Validation is where the model earns its keep, turning a static estimate into a monthly control over what actually gets paid.
Validation only works when it is owned. A named person inside the separation management office, backed by finance, should run the checklist every cycle and approve only the lines that pass. Without a single owner the task falls between teams, the invoice gets paid to keep the relationship smooth, and the discipline collapses in the first busy month.
Every disputed line goes into a log before payment, with the service, the amount, the failed test, and the date raised. Logging the dispute before payment matters because it puts the challenge on the record while the buyer still holds the money. A charge questioned months later, after it has been paid, is far harder to claw back than a charge held at the point of invoice.
Tie the routine to a hard date in the governance calendar, before the payment run, so validation always happens before money moves. Where the pattern of errors is large or the seller resists correction, the dispute belongs in formal governance, and a structured renegotiation of the terms is often the cleaner fix than fighting the same line every month.
TSA charge validation is the monthly discipline of testing every line on the seller invoice against the agreement. Each charge is checked against the service catalog scope, the agreed rate, the actual volume consumed, and the agreed cost basis. The aim is to confirm the buyer pays only for services it receives at the price the agreement sets.
Because seller billing systems are built for internal allocation, not for a contract with a buyer. Charges drift as services are added, volumes change, and exited services keep appearing. Without monthly validation, small errors compound across the life of the agreement and the buyer pays for capacity and overhead it no longer uses.
The most common errors are charges for services that were never in the catalog, charges that continue after a service has exited, volume that does not match actual consumption, mark-up applied above the agreed rate, and allocated overhead dressed up as service cost. Each is recoverable when the buyer holds the invoice against the agreement.
A named owner inside the separation management office, supported by finance, should run validation every cycle against the service catalog and the cost model. The owner approves only the lines that pass and logs every disputed charge into governance, so the dispute is on the record before payment rather than raised months later.
The baseline every validation cycle should test against.
Read the article →Catch charge drift against the plan, every cycle.
Read the article →Why the cost basis is the test that recovers the most.
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