The brief lands in your inbox. The brand wants trial among new shoppers, repeat purchase from existing customers, a data capture mechanic, social engagement, and — while we’re at it — a retailer sell-in story for the upcoming range review. All from one promotion. With a modest budget.
If you’ve worked in promotional marketing for any length of time, you’ve seen this brief. You might have written it. And if you’re being honest, you probably already know the problem: a promotion that tries to do five things tends to do none of them well.
This is where the One Job Rule comes in. It’s a concept we use at Trevor Services — and one we wrote about in The Shelf Truth — because it keeps showing up as the single biggest predictor of whether a promotion will actually deliver.
What is the One Job Rule?
The idea is straightforward: every promotion should have one primary commercial objective. Not one category of objectives. One job.
In The Shelf Truth, we frame the five promotional jobs as:
- Breaker — drive trial among new buyers
- Builder — increase purchase frequency among existing buyers
- Loader — grow basket size or volume per transaction
- Harvest — capture first-party data
- Keeper — protect or reward existing loyal customers
Each of these jobs points you toward a different mechanic, a different prize structure, a different entry path, and a different way of measuring success. When you try to load multiple jobs into a single campaign, each one compromises the others.
Why does multi-objective thinking persist?
It’s rarely because the marketing team doesn’t understand focus. It’s usually because the brief reflects competing internal pressures — the brand manager wants trial, the trade marketing team needs a sell-in story, the digital team wants email sign-ups, and the CMO wants to report on all of it.
The result is a promotion designed by committee, optimised for nobody. And the numbers bear this out. Research from Accuris and historical Nielsen analysis suggests that roughly 59–60% of trade promotions in key FMCG markets don’t break even. The reasons are varied — cannibalization, stockpiling, poor measurement — but a lack of objective clarity sits underneath many of them.
When you don’t know what the promotion is supposed to achieve, you can’t design the mechanic to achieve it, and you certainly can’t measure whether it worked.
What happens when you pick one job?
Choosing a single objective isn’t about limiting ambition. It’s about giving the promotion enough design clarity to actually succeed.
Take trial (the Breaker job). If your one job is getting a product into the hands of people who haven’t bought it before, that shapes every decision. You’d likely choose a low-friction mechanic — perhaps a gift with purchase or an instant win — because you need the barrier to entry to be almost nothing. The 3-Second Equation from The Shelf Truth describes this calculation: Reward + Belief, divided by Friction. For a trial-driving promotion, you need to minimise friction above all else.
Now consider loyalty (the Keeper job). The design looks completely different. You might run a collect-to-win or a tiered cashback that rewards repeat purchase over a sustained period. Higher friction is acceptable — even desirable — because you’re filtering for committed buyers, not casting a wide net.
Try running both mechanics in the same campaign and you get a muddy experience. The entry path is either too easy to reward loyalty or too complex to attract trialists. The prize pool gets split. The messaging tries to speak to everyone and connects with no one.
How to apply the One Job Rule in practice
Start by asking the question that matters: what commercial outcome justifies this promotional spend? Not what would be nice to achieve. What has to happen for this promotion to be worth the investment.
If the answer is “we need to shift 10,000 units of a new SKU into first-time hands,” that’s trial. Build a trial promotion. If the answer is “we need our top 20% of buyers to increase frequency by one occasion per quarter,” that’s frequency. Build a frequency promotion.
Here’s a practical framework for pressure-testing your brief:
Does the objective pass the measurement test?
If you can’t define exactly how you’ll measure success before the campaign launches, the objective isn’t clear enough. “Build brand awareness” is not a promotional objective — it’s an advertising objective. Promotions are tactical, transactional instruments. They should connect to a measurable commercial outcome: units sold, new buyers acquired, data captured, basket value increased.
As the IPA’s Marketing Effectiveness Roadmap emphasises, the choice of objectives and metrics is crucial to effectiveness. A tight focus makes progress more likely — and makes it possible to know whether you got there.
Does the mechanic match the job?
Once the job is clear, the mechanic should follow naturally. The Shelf Truth maps this relationship through the lens of Hope vs. Greed — what we call the Two Pilots. The Gambler wants dopamine: instant wins, prize draws, the thrill of chance. The Accountant wants certainty: cashback, guaranteed gifts, known value.
A trial promotion often benefits from a Gambler mechanic. A big, attention-grabbing prize creates the initial interest needed to get a new buyer to engage. But a frequency promotion usually needs an Accountant mechanic — something that rewards sustained behaviour, not a single lucky moment.
Mismatching the mechanic to the job is one of the most common errors in promotional planning, and it almost always traces back to unclear objectives.
Can you explain it in one sentence to a retailer?
This is the practical test. In The Shelf Truth, we call this the S.O.S. Framework — Simple, Operational, Sales. If you can’t explain to a category manager at Coles or Woolworths what the promotion does, how it works operationally, and why it will drive their sales, the brief is too complicated.
Promotions that try to achieve multiple objectives tend to fail this test. “It’s an instant win that also collects data and drives repeat purchase through a secondary mechanic” makes a category manager’s eyes glaze over. “Scan the code, see if you’ve won” — that’s a promotion they’ll support.
What about secondary benefits?
Picking one job doesn’t mean you ignore everything else. A well-designed trial promotion will naturally capture some data through the entry process. A frequency campaign will produce useful insights about purchase patterns. These secondary benefits are real, but they shouldn’t drive the design.
Think of it this way: the primary objective shapes the mechanic, the prize architecture, the entry path, and the measurement framework. Secondary outcomes are welcome byproducts, not design inputs.
This is especially relevant when it comes to data capture, which has a habit of muscling its way into every brief. Yes, first-party data is valuable. But adding three extra form fields to capture it can increase friction to the point where the primary objective — whether that’s trial, frequency, or basket loading — is materially undermined. As a general principle, every additional form field costs roughly 10% of entries in compounding drop-off. That’s a steep price for data you may or may not use.
The Kill Sheet test
At Trevor Services, we use what we call the Kill Sheet — a 15-minute diagnostic that stress-tests whether a promotion will work before a dollar is spent. The first question on it is always: what is the one job this promotion needs to do?
If the answer takes more than one sentence, or if it includes the word “and,” the promotion isn’t ready to build. That doesn’t mean the ambition is wrong — it means the brief needs to be split into separate campaigns, each with its own job, its own mechanic, and its own budget.
Two focused promotions will almost always outperform one unfocused one, even on a smaller per-campaign budget. The economics of promotional marketing reward clarity.
Getting this right before you build
The best time to apply the One Job Rule is at the briefing stage — before creative is developed, before permits are lodged, before the agency starts scoping mechanics. It’s a strategic decision, not a creative one.
If you’re building a promotional calendar for the next quarter and find yourself writing briefs with three or four objectives per campaign, step back. Ask which job each promotion is really doing. Split where necessary. And measure each campaign against the one thing it was designed to achieve.
If you’d like to pressure-test an upcoming promotion against the One Job Rule, we’re happy to walk through it with you.
