A retainer is an agreement to reserve a quantity of an agency's attention each month. It suits work that never finishes and it makes drift easy: both sides settle into a rhythm, the reports arrive, and nobody asks whether the hours are still going to the most valuable work available.
What a retainer should specify
The hours or the deliverables, the seniority mix, what is included and excluded, the reporting cadence, and who the named team is. A retainer specified only as a monthly figure and a list of services is one where scope disputes are inevitable, usually in month four when someone asks for something the other side considers extra.
Rollover and the quarterly balance
Unused hours are a recurring argument. Unlimited rollover creates an awkward liability for the agency; a rigid monthly reset punishes a client for a quiet month. A quarterly balance is the usual compromise and it should be written down rather than settled by goodwill, which runs out precisely when it is needed.
The review that can change things
A quarterly review with the authority to reallocate the retainer is what prevents drift. Without it, the shape of the work at signature persists long after the priority moved. The healthiest relationships change what they do every few quarters while the fee stays stable.
Notice and what it obliges
Agree the notice period and, more importantly, what it requires: which accounts and assets transfer, whether work in progress is completed, and how documentation is handed over. This is easy to settle while both sides are optimistic and always contested afterwards.
Questions people ask about agency retainer
How long should a retainer run initially?
Long enough for the work to show something, with a genuine review before renewal. Search and content need longer than paid media.
Should unused hours roll over?
A quarterly balance is the usual compromise. Whatever is agreed should be in the contract rather than left to goodwill.
How do I know a retainer is still earning?
Ask what changed last quarter and what next quarter will do differently. A supplier describing the same activities every month is maintaining rather than improving.