Agencies sell SEO in two main shapes: a recurring monthly retainer, or a defined project with a start and end. Neither is inherently better. The right one depends on the kind of work, how well you know the problem, and how much flexibility you need.
What each model is
Retainer. You pay a recurring fee in exchange for an ongoing allocation of effort: a set of deliverables, a pool of hours, or access to a team. Scope usually flexes within the pool as priorities change.
Project. You pay for a specific, finite outcome: a technical audit, a site migration, a content strategy, a category-page rebuild. Deliverables and acceptance criteria are defined up front.
When a retainer fits
- The work is continuous by nature. Content publishing, ongoing technical monitoring, link and PR programs, iterative testing.
- Search performance responds to cumulative effort. Compounding work is poorly served by one-off sprints.
- You want a standing team who learns your business and can react to changes, such as algorithm updates or a competitor's move.
- Priorities will shift. A pool lets the agency move effort where it matters without renegotiating.
When a project fits
- The problem is well-defined. A migration, a one-time cleanup, an international structure.
- You want to test an agency before a longer commitment. A discrete audit shows how they think.
- You have strong in-house execution and need a plan or specialist review rather than hands-on work. See Agency vs Freelancer vs In-House Team.
- Budget is capped and you need certainty about the total spend.
Risks of each
| Retainer risk | Project risk | |
|---|---|---|
| Scope | Vague deliverables and "busy work" | Scope creep disputes, change orders |
| Cost | Paying for activity, not impact | Underestimated complexity, overruns |
| Continuity | Lock-in with weak exit terms | Knowledge leaves when project ends |
| Accountability | Hard to tell if effort matches fee | Acceptance criteria may be too narrow |
How to make a retainer accountable
A retainer should read less like a subscription and more like a work plan. Ask for:
- A named monthly deliverable list, or a clear allocation by workstream.
- A backlog and priority review at a regular interval, with the reasoning for what is chosen.
- Time or activity reporting at a level that lets you see where the effort went.
- A review point, such as a quarterly check, where either side can adjust or end the engagement.
- Notice terms you can live with. Long minimum terms should be justified by setup costs, not just sales preference.
How to make a project accountable
- Written deliverables and acceptance criteria.
- A clear statement of what is excluded.
- How changes are priced and approved.
- Handover: documentation, training, and the format in which you receive outputs.
- Who is responsible for implementation, and what happens if your developers cannot deliver.
Hybrid structures
Many engagements combine both: a fixed-fee audit and roadmap, followed by a retainer to execute it. This lets you judge diagnostic quality before committing to ongoing spend. Another pattern is a lean retainer for monitoring and content, with separate fixed-fee projects for large technical changes such as a replatform; see SEO Migration Checklist for Buyers.
Be careful with performance-based fees
Models that tie fees to rankings or traffic can look safe but contain pitfalls. Check how success is defined, which keywords or pages count, who has measurement access, and whether the model encourages tactics that boost the metric at the expense of business results. Outcomes also depend on factors the agency does not control, such as your product, pricing and site speed to implement fixes.
Questions to ask
- What exactly do I receive each month, or at project completion?
- How are changes in scope handled and priced?
- What is the minimum term and how can I exit?
- Who owns the documents, content and accounts created?
- What happens at the end: handover, transition support?
More are in Questions to Ask Before Signing.
Evidence matters more than the model
A well-run retainer beats a badly specified project and the reverse. Look at the quality of the agency's own materials. Listings on this site show whether a claim comes from the agency's own site, a published case study or independent corroboration, and sponsorship never buys verification. Compare pricing structures in the context of what an agency costs and use the comparison tools to line up shortlisted options.