The contract initiation fee is a one-time charge Upwork makes to a client when a new marketplace contract starts, set by Upwork at an amount that varies with the contract and paid on top of the marketplace fee on each payment.
Clients on Upwork pay in two ways. The client marketplace fee is a percentage of every payment to a freelancer or agency; the contract initiation fee is a flat amount charged once, when the contract is first funded or the first hourly invoice is raised. Upwork introduced it after the move to a flat freelancer fee, as part of a broader shift of cost from the talent side to the client side. The amount is set by Upwork, is stated in the Help Center, varies with the size of the contract and may change; it does not apply to every client plan, and Upwork Enterprise clients pay under their own agreements.
The freelancer never sees the fee and does not pay it; it appears on the client's invoice only. It does, though, shape client behaviour. A flat fee per contract weighs more on a small contract than a large one, so some clients prefer one longer contract with several milestones to a string of short ones, and the rehire of a known freelancer becomes marginally more expensive than extending an open contract.
From the outside the fee is one of the components of Upwork's blended take rate: client fees are part of why the rate can rise while the headline freelancer fee stays at 10%. The line it belongs to in Upwork Inc.'s reporting is marketplace revenue.
How Upwork Insights uses it
This term describes Upwork's own rules or product rather than a figure the index measures; the pages that do carry live figures are the stats and rate pages.