A retainer is a standing monthly engagement: the client pays a fixed fee — say $8,000 a month — for an agreed amount of capacity, such as 80 hours or half of a senior engineer's week. It sits between the two classic contract models: time and materials (pay for actual hours) and fixed price (pay for a defined scope).
What the fee buys is availability, which makes retainers both attractive and risky:
- For the vendor — predictable recurring revenue and smoother capacity planning; the engagement isn't re-sold every month.
- For the client — a reserved team that doesn't disappear between projects, usually at a slightly better effective rate.
- The risk — silent over-servicing. Retainer hours are the easiest in the company to stop tracking, and a "40-hour" retainer quietly consuming 60 hours is negative margin nobody approved.
Three habits keep a retainer healthy: log hours against it exactly as on T&M — consumption against the retained capacity is the health metric; review that consumption monthly (persistent under-use invites churn, persistent over-use is a repricing conversation, not heroism); and write the rollover rule down — do unused hours carry into next month or expire?
In Helia, retainer is one of the per-project billing models alongside time and materials and fixed price: the project carries its monthly retainer amount, timesheet hours are logged against it as usual, and the invoice goes out as a flat monthly line rather than hours × rate.