Media buying agency: your money passes through their hands, so buy the transparency terms before you buy the media plan

A media buying agency negotiates and places your advertising with the people who own the inventory: broadcasters, publishers, platforms, out of home operators, podcast and retail media networks. The work is pricing, negotiation, scheduling, trafficking the creative, verifying that what you paid for ran, and reconciling the invoices. The structural fact that should shape the contract is this: most of the money you commit does not stay with the agency, it flows through them to the media owner. So the terms that matter are not about strategy or creativity. They are about what happens to your budget in transit and whether you can see it.

Buying, planning, and why the split matters to the invoice

Planning decides where the money goes: the audience, the channels that reach them, the budget split, the schedule and the measure. Buying executes that plan at the best price and terms available, then proves it ran. The two are usually sold together and are separately priceable, which is worth knowing, since plenty of advertisers buy a plan once a year as a project and execution monthly.

Three shapes of supplier do the work. Full service agencies plan and buy across every channel. Specialists concentrate on one area, such as out of home, broadcast or retail media, and negotiate better inside it. Trading desks buy digital display, video and connected television through automated exchanges, where the fee structure needs most scrutiny because more layers sit between your dollar and the impression.

Commission, fees, and what they add up to

The ranges below are my own read of the US market, drawn from fee discussions and contract scopes rather than a published benchmark. Commission in media falls steeply with volume, more steeply than in most agency categories, so the comparison that matters is against your own spend level.

• Commission on media: roughly 8 to 15 per cent under 500,000 dollars of annual spend, 4 to 8 per cent between one and ten million, and 2 to 5 per cent above twenty five million, where the fee is usually built on staffing rather than a percentage at all.
• Flat monthly fee instead of commission: 5,000 to 30,000 dollars a month for a mid market advertiser, by channel count and reporting load.
• Staffing based retainer: priced per full time equivalent. A fully loaded buyer or planner costs an agency somewhere between 120,000 and 200,000 dollars a year in the US once salary, benefits, tools and overhead are counted, and the retainer is that figure plus a margin of roughly fifteen to twenty five per cent, split across the year and across the clients that person covers.
• Planning only, as a project: 15,000 to 60,000 dollars for an annual plan with audience research, channel modelling and a flighting schedule.
• Minimum engagement: many shops will not take an account below roughly 25,000 to 50,000 dollars a month in spend, because the commission does not cover the work. Below that, direct buying or a specialist freelancer serves you better than a junior buyer with ten other accounts.
• Technology fees on programmatic: the demand side platform, verification, brand safety and data layers commonly take 10 to 20 per cent of working media between them, separate from the agency fee.

Add the fee and the technology layers together and you have the most useful number in this category: the share of your budget that becomes an impression somebody could see. Ask every agency to state it as a percentage for a representative campaign. A firm that answers confidently has nothing to hide, and the answer varies enough between suppliers to decide a pitch.

Where margin hides, and the terms that expose it

None of what follows is improper in itself, and all of it is standard practice somewhere. What is unreasonable is not being told.

Practice	What it means	The contract term to ask for
Principal media	The agency buys inventory in bulk for its own account and resells it to you at its own price rather than acting as your agent	Written notice before any principal based buy, with your prior approval
Rebates and volume agreements	Media owners pay the agency for hitting annual volume across all its clients, and your spend helped earn it	A statement of whether rebates are received and how the share attributable to your spend is handled
Arbitrage in programmatic	A fixed cost per thousand impressions quoted to you while the agency buys cheaper on the exchange and keeps the difference	Log level data access, or a declared fee on top of disclosed media cost
Unspent budget and credits	Make goods, cancellations and underdelivery credits that never come back	Quarterly reconciliation, credits returned within a named number of days

Two clauses do most of the work. An audit right, giving you or your accountants access to the records and invoices for your account on reasonable notice, is normal in large advertiser contracts and reasonable in small ones. And a plain statement of capacity: whether the agency acts as your agent, buying for you and disclosing what it paid, or as a principal selling you inventory it owns. Those are different legal relationships, and a firm should be able to say in one sentence which applies to each part of your plan.

Proving the advertising ran

Verification is half of what a buying agency is for and the half clients forget to ask about.

• Post buy reconciliation. A written comparison of what was ordered against what was delivered, with make goods for shortfalls, signed off before you pay.
• Independent measurement on digital. Viewability, invalid traffic and brand safety measured by a third party rather than reported by the seller. Ask who pays, and whether the fee sits inside the media budget.
• Inclusion and exclusion lists for programmatic, reviewed monthly, with the placement report open to you. A domain report you may not see is the clearest warning sign in this business.
• Disclosure on native formats. Advertising built to look like editorial has to be identifiable as advertising, a long standing position of the Federal Trade Commission, and the advertiser carries that duty. Ask to see the label treatment before a sponsored placement runs.

Four questions before you hand over a budget

• What share of a representative budget reaches working media? A number, with the fee and technology layers itemised.
• Which media owners have you renegotiated with this quarter, and what did you get? Buying is a negotiating job and the answers are specific or they are nothing.
• Show me a reconciliation report from a real campaign, client details removed. You want underdelivery recorded and resolved, which is what a working process looks like.
• What comes out of the plan if the budget falls by a third? Reach and frequency logic in the answer means they understand media. Trimming every line proportionally does not.

When buying media through an agency is not the right call

• Your spend sits entirely in self service platforms. Search and social bought through the ad managers need an operator rather than a buyer, which is a performance marketing engagement priced differently.
• Spend above roughly ten million a year in a stable mix. An in house buying team plus an independent auditor becomes a live option, and several large advertisers have moved that way for the transparency reasons above.
• You have no creative ready. Booked inventory with nothing to run in it is the most wasteful position in advertising. Settle the creative timeline before signing anything with a flight date.

Contract questions advertisers raise about media buying

Is a percentage of media spend ever the right structure?

A flat fee or a staffing based retainer is cleaner, because the agency's income stops moving with a recommendation to spend more. Commission stays common at lower spend levels and works well enough with two additions: a declining rate at named thresholds, and a written statement that third party costs pass through at cost.

Who should hold the contracts with media owners?

Where you can, contract directly with the owner and have the agency act as your buying agent on disclosed terms. That keeps your credit relationship, your rates and your reconciliation visible. Where it must contract as principal, get it stated in writing with its own approval step.

How much notice does a media contract need?

Sixty to ninety days, longer than in most agency categories, because media is booked ahead and somebody has to see out the commitments already placed. Attach a handover schedule of booked flights, outstanding credits, placement lists and reconciliation status.

What has to be in the post buy reporting?

Spend against plan by channel and by media owner, delivery against ordered impressions or spots, fee and technology costs shown apart from working media, reach and frequency against plan, outstanding credits, and the negotiations opened or closed that month. Reach and frequency with no cost breakdown is a presentation rather than a report.

The placement nobody can sell you

Every line on a media plan is inventory somebody owns and will sell. There is now a place your brand appears where no inventory exists and no rate card applies. A buyer asks ChatGPT, Gemini, Perplexity, Claude or Google AI Overviews which brand to pick in your category and the reply names two or three. It behaves like the most valuable slot in the plan, arriving as a recommendation rather than an advertisement, and no budget books it. What decides it is the text about your business a model can find and trust: your own pages, press coverage, reviews, directories, the sites that compare suppliers. For a discipline built on share of voice, that is a share of voice figure missing from the report. AI Knows Us reports it the way a post buy report reads: what ran, where it came from, and who else was in it: aiknowsus.com.