TSA overruns almost never arrive as a single, obvious failure. They arrive as a stream of small, individually-defensible decisions — one more month on IT, a slightly delayed payroll cutover, a "we'll sort the last two services out next quarter" — each of which looks minor in isolation. The cost only becomes visible in aggregate, usually well after the point where it could have been prevented cheaply.
Extension pricing is not neutral
TSA pricing structures are typically set once, at signing, based on the assumption that the relationship is short-term by design. When a workstream runs past its original term, extensions are rarely priced at the original rate. Analysis of carve-out TSA structures shows extensions beyond the base term commonly carry a 5 to 15 percent monthly premium over baseline pricing — a cost curve that punishes delay specifically, on top of whatever the underlying service itself already cost.
That premium exists because the seller's incentive changes the moment the base term ends. What was a favor built into the deal price becomes a standalone commercial relationship, priced accordingly.
The gap is usually structural, not accidental
Industry analysis of why TSAs overrun points to a specific, repeatable failure pattern rather than a series of unrelated one-off problems. The most common root cause: the TSA term was set against the legal closing calendar — what both sides needed the number to be in order to sign — rather than against the actual separation plan's realistic timeline. Everyone involved often already suspects, at signing, that the term is too short. It gets signed anyway, because closing on schedule matters more in the room than the operational reality six months out.
The second most common cause is scope discovered after close: dependencies and shared systems that weren't fully inventoried before the deal, surfacing mid-TSA as newly "found" services that then get priced at extension rates rather than the base agreement's rates.
Carve-out complexity compounds the exposure
Separation cost is also frequently underestimated at the outset. McKinsey's analysis of carve-out cost structures has found that standalone costs for services previously delivered at parent-company scale can run as much as 200 percent higher once replicated independently — a shared-services allocation that looked like $10 million in the parent's books can cost $20 million to stand up alone. That gap, if not modeled into the purchase price and the TSA exit plan from the start, tends to surface mid-term as a funding scramble rather than a planned cost.
The value impact is measurable at the fund level. Bain's longitudinal data on carve-out outcomes since 2012 shows an average return of roughly 1.5x MOIC, with top-quartile execution — carve-outs where separation was managed well — delivering closer to 2.5x. That gap between average and top-quartile execution is, in large part, a story about how well the TSA period was managed.
Why the fix usually isn't "negotiate a longer TSA"
The instinctive response to overrun risk is to negotiate more time upfront. In practice, this often just delays the same problem: a longer TSA still lacks the defined exit criteria, service-level ownership, and acceptance testing that actually determine whether a service is transitioned or merely "still running." Some carve-out programs have shown that with disciplined, pre-close readiness planning, TSA exit timelines can be compressed dramatically — advisory analysis has pointed to exits completed in as little as 2 to 3 months post-close where the separation plan, rather than the legal calendar, drove the timeline from day one.
The distinguishing factor isn't TSA duration. It's whether every service inside the TSA has a named owner, a defined completion standard, a tracked exit date, and — critically — a live view of where each workstream actually stands relative to that date, rather than a static document reviewed only when someone remembers to check it.
The practical takeaway
A TSA that's tracked service-by-service, with real visibility into which workstreams are on schedule and which are quietly drifting, is fundamentally a different risk profile than one reviewed at the start and then revisited only when a deadline is already missed. The overrun cost isn't really a pricing problem. It's a visibility problem that shows up as a pricing problem several months too late to do anything about cheaply.
Sources: McKinsey & Company carve-out cost analysis, Bain & Company carve-out MOIC research (data since 2012), and industry TSA structuring and pricing analysis from BD Emerson, KPMG, and Dealroom.