GROSS. — free commercial calculators for UK FMCG brand teams

What a promotion actually costs

Supplier funding mechanics, the uplift myth, cannibalised base sales and the payback test — what UK grocery promotions really cost, with a free calculator to run yours.

Funding off invoice, the uplift with the widest error bars in the building, and the payback test nobody runs. Worked openly.

The default convention in UK grocery is that promotions are supplier-funded: the retailer keeps their margin percentage, and the consumer price cut comes off the brand's invoice. On a 25%-off deal, that means your gross sales value × 25% is deducted from your line for every promoted week. The shelf says the retailer is being generous; the ledger says you are.

That funding is only the visible cost. Around it sit the less visible ones: the extra stock bought early to service the uplift, the margin given away on volume that would have sold anyway, and any fixed contributions — gate fees, feature space, retail media — attached to the activity.

The uplift is the soft number

Every promo case rests on an uplift assumption, and the uplift is the number with the widest error bars in the building. Some of the promoted volume is genuinely incremental; some is your own base sales bought at a discount; some is shoppers stocking up on a product they would have bought next month at full price. A promotion that doubles volume can still lose money if half of that volume was coming anyway.

The honest test is arithmetic, not optimism: incremental units × margin on those units, set against the full funding cost plus any fixed fees. If the deal only pays back at the top of the uplift range, it does not pay back.

When promotions are worth it anyway

None of this means never promote. Promotions buy things the base rate of sale cannot: trial from new shoppers, defence of shelf space at range review, velocity data that supports distribution arguments. The discipline is to name what you are buying and its price before you sign — a promotion run as a strategic investment with a known cost is a decision; the same promotion run because the buyer asked is a leak.

The rule of thumb the trade actually uses: if a promotion cannot pay back within the deal period plus one buying cycle, it is brand investment — and brand investment should appear in the plan as brand investment, not disappear into the trade line.

Asked a lot

Who pays for supermarket promotions?

Usually the brand, through supplier funding: the retailer keeps their margin percentage and the discount is deducted from the supplier's invoice for every promoted week. Retailer-funded promotions exist but are the exception.

What uplift should I expect from a promotion?

It varies enormously by mechanic, category and depth of cut — deep price cuts on impulse categories can multiply volume, shallow cuts on considered purchases barely move it. Treat any single figure as an assumption to stress-test, and model the case where the uplift halves.

Do supermarket promotions make money for brands?

Sometimes — when the incremental margin clears the funding plus fixed costs, or when the promotion buys something strategic (trial, distribution defence) at a price you named in advance. Run the payback before you sign; most disappointing promotions were knowable in advance.

What is trade spend?

The money that flows from brand to retailer around the trading relationship: promotional funding, retrospective discounts, back margin, range support. It nets off revenue (it is not marketing) and typically consumes 10–30% of a UK brand's invoiced sales.

The other calculators

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• The Stock Answer — What to order, and when, before you run out. A weekly supply plan that follows your promo calendar, in whole c
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• The Ledger No. 001 — Your margin is your insurance. The minimum margin that survives a halved rate of sale, worked in full.
• The Guides — The long reads behind the calculators: retailer margin, gross-to-net, FBA fees and margin benchmarks, written
• How retailer margin actually works — Front margin, back margin, margin vs mark-up and the wholesaler layer — with the arithmetic shown.
• Gross-to-net: where your revenue goes — GSV, NSV, promo funding and back margin — the waterfall between invoice and bank, and what a healthy one looks
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• FMCG margin benchmarks — Indicative UK brand gross-margin ranges by category, measured on the right base and honest about being ranges.
• Payment terms in UK grocery — Sixty days is not a detail — it is working capital, and it is yours. The debtor-day maths, the shelf-fill trap
• The Rate Card — Every default in GROSS., what it is, when it was checked and where it comes from. The maths is only as good as

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