How do you tell if your marketing agency is any good?

The assumption inside almost every version of this question is that a good agency is one that behaves well: communicates promptly, explains its thinking, admits when something has not worked. That is what the first page of results grades. It is the wrong instrument, because an agency can improve all of it inside one notice period, and none of it says anything about the nine months before.

A managing partner at a fourteen person accountancy practice reads an eleven page report every month. Impressions are up, positions have moved, the content calendar is full, the domain authority score has risen two points, and she cannot name one client who arrived through any of it. Nothing in it is false. Every figure came from the party being assessed, which is why nine months of it has not answered the question a UK partner actually has.

Judge the agency on evidence it cannot edit

The useful checks are the ones the agency cannot influence between now and the moment you run them.

An agency can add a strategy slide and start returning calls the same day, inside a single notice period. What it cannot change is what is already recorded in Google's ad library, or whose name sits on the account. The four checks below are sorted on that basis.

The checks that need nobody's permission

Google and Meta both publish a searchable library of the ads an advertiser is running, and your own campaigns are in it. Google's Ads Transparency Center can be searched by advertiser or website name and filtered by date and location, and it covers ads served across Google Search and YouTube. Meta's Ad Library does the same for Facebook and Instagram, and shows the ads any Page currently has active. Put your own firm's name into both.

Most of the time you will find what you were told. What it settles is the problem UK firms actually hit: a campaign quietly paused in month three for a declined card or a policy disapproval, still reported as managed. Ten minutes, and the only check here that saves money the same week.

The website works the same way. The Internet Archive holds dated captures of most public sites, so pages an agency says it built in April are either in the April captures or they are not. A site: search on your own domain is the companion check: it shows what Google indexed rather than what was published, and unindexed content is not yet working for anybody.

Then ask last month's report one question

Go through it and mark every figure for who produced it. Impressions, keyword positions, reach, posts published and click-through rate are agency outputs. Enquiries received, calls booked, proposals sent and clients signed are not. A report can be honest and detailed and still tell you nothing, if every figure sits on the first side of that line.

The fix is cheap: agree two outcome figures your own team records and require them in the report alongside the activity. An agency that has been asking for those figures for six months without receiving them is telling you something about your own practice.

Whose name is on the accounts

A firm that cannot log into its own advertising account has not found a reporting problem. It has found its exit problem.

Google Search Console is free, and reports how a site appears in Google Search. Analytics is free. The advertising account bills your firm directly. None of the evidence is a paid extra, so if you cannot reach it, the property is held in the agency's name rather than yours.

The right arrangement is dull and takes an email. Your firm owns each property and the agency is added as a user. Ownership survives the relationship and user access does not, a difference that only shows on the day you want it to. Where the agency also handles personal data belonging to your clients, UK data protection law requires a written contract, and the ICO sets out what it has to contain. A lot of firms find they do not have one. Our piece on what to walk away from sorts this as terminal rather than negotiable, for the same reason: no clause you write next month recovers an account you never owned.

Read the clock the way Google publishes it

Google's own guidance for anyone hiring search help says it takes four months to a year from making changes to seeing the benefit. That is published by Google, not an agency's excuse, and it cuts both ways. A partner judging a search retainer at month two is judging noise. A partner ten months in with no movement in any leading indicator is not being impatient, and an agency quoting the same line at that point is quoting the half that suits it.

Paid work runs on a different clock: a campaign either serves and receives clicks inside the first fortnight or the setup is wrong. Judging both disciplines on one timeline is where retainers go wrong, usually because they were sold to the practice as one line item.

When not to change agency yet

Two findings look like agency failure and are not. The first is a brief that changed twice and was never rewritten, which produces the drifting activity report above. The second is an approval bottleneck: where nothing leaves your office inside a fortnight, the agency bills you for the waiting. Both are yours to fix, and a new supplier inherits them unchanged.

There is also the case where a firm should not appoint anybody at all. If nobody in the practice has recorded what a new client is worth over the time they stay, no supplier can be assessed and no replacement will be either. An afternoon with your fee ledger settles it, and it beats another pitch process.

Where the four checks come back clean and the results are still thin, the honest answer is usually a scope problem rather than a supplier problem. The questions in what to ask a digital agency, and how to verify each answer work as well on an incumbent as on a candidate. Our page for professional services firms sets out what we assess before recommending anyone, and the wider guide to choosing a digital agency covers the decision this post only reviews.