Co-managed IT is what a business buys when it already has somebody internal and that person is the bottleneck rather than the problem. Instead of replacing them, the provider supplies what one person cannot: monitoring tooling that costs more than a salary to license, cover at night and at weekends, second-line depth on the days something genuinely hard breaks, and someone to hand the tedious repetitive work to. It is the most common shape above roughly fifty staff and the easiest to get wrong.
What each side normally takes
The internal person keeps the relationships, the projects, the vendor conversations and the judgement calls, because those need somebody who knows the business. The provider takes the tooling, patching, monitoring, backup administration, first-line tickets and out-of-hours cover, because those need scale and a rota. The division works when it follows that logic and fails when it is drawn by cost, which usually means splitting a single job in half and leaving nobody accountable for it.
The failure mode is a ticket nobody owns
Every co-managed arrangement that goes wrong goes wrong the same way: a problem arrives that sits on the boundary, both sides believe the other has it, and it ages quietly until somebody senior notices. The fix is not goodwill, it is a written escalation path with a default owner for anything unassigned, and one shared ticket queue rather than two systems that have to be reconciled by a human.
What to check before signing
Whose tooling is it and what happens to the data in it if the arrangement ends. Who holds the administrative credentials, and whether your own person retains them. Whether the provider's monitoring can be read by your internal staff or only by the provider. And which tickets count against the contract, because a per-seat fee with an internal team filtering the easy ones is a different economic proposition to one taking everything raw.
Questions people ask about co-managed it
What is co-managed IT?
An arrangement where a business keeps its own IT person or team and buys tooling, depth and out-of-hours cover from a provider around them, rather than outsourcing the function entirely.
At what size does co-managed make sense?
Commonly above about fifty staff, where there is enough work to justify somebody internal but not enough to justify a team with a night rota and enterprise tooling.
Who should hold the administrative credentials?
Your business, always, with the provider granted its own named accounts. A co-managed arrangement where only the provider can administer the estate is an outsourced arrangement with extra steps.