Fixed Per Product
An incentive structure that pays a flat fee per unit of a product sold. Multiplies by quantity.
Requires Siren Essentials
WordPress plugin and Siren Cloud
Last updated: October 26, 2026
Fixed Per Product is an incentive structure that pays a flat fee for each unit of a qualifying product sold. Unlike Fixed Per Transaction, which pays once per conversion, this structure multiplies the flat fee by the quantity of units in the transaction.
When a customer converts, Siren counts qualifying units across the transaction’s line items and creates an obligation for the unit count times the configured per-unit amount. Line item filters determine which products count. To pay each product owner per unit of their own products, use “Every engagement wins” and tick “Collaborator Owned Products Only”. Without the filter, each owner is paid on every unit in the order.
How it works
If the incentive is set to $5 per unit and a customer buys 8 units of a qualifying product in a single order, the commission is $40. If they buy 1 unit, it’s $5. Quantity drives the payout.
A program that pays renewals pays the per-unit amount on each renewal order’s units. On LifterLMS, a free trial sign-up pays too, whether or not the trial turns into a paid subscription. See what a renewal pays.
This structure is a good fit when unit profit is roughly constant. If each product unit yields the same margin, a flat per-unit commission gives you predictable cost-per-sale math. You can calculate exactly what a collaborator earns for any cart composition without worrying about fluctuating percentages.
Where this works
This works best for stores with uniform product pricing and stable per-unit margins (books, standardized supplements, consumer electronics with fixed retail prices). It also suits subscription services with flat monthly pricing, where you can easily compute a sustainable per-signup payout based on average customer lifetime value.
The fixed rate affiliate program recipe uses a flat dollar payout per sale, which works well whenever the business math on each unit is predictable enough to set a sustainable commission up front.
When to avoid this
If you sell products at wildly different price points and want affiliates to focus on higher-value items, use Percentage of Transaction instead. A flat per-unit fee treats a $10 product and a $500 product the same, which usually doesn’t match your actual margin on either.
It’s also not a fit for service businesses or programs where the thing being sold isn’t a discrete product unit. If you’re paying for leads or single-transaction outcomes without a per-unit concept, Fixed Per Transaction or Percentage of Transaction will fit better. A subscription fits when each renewal is one unit of one product. On Siren Cloud, each line of a Stripe invoice counts as one unit, so a metered or multi-line invoice pays once per line.