Quantity discount - Zenskar Documentation

How to set up a basic quantity discount

On the line item, add a quantity discount.
Set value to the number of discounted units per cycle.
Set cadence to how often the pool refreshes (for example, P1M for monthly), or leave it unset so each billing period independently gets the full value.
Optionally set a label for how the discount shows on the invoice.
Save. Unused units expire at each cadence boundary — there’s no carryover in the current phase.

Set cadence to the window you want the pool to refresh on.
If the cadence is longer than the billing period (for example, quarterly cadence with monthly billing), the pool is shared across those billing periods and depletes chronologically — earlier periods draw from the pool first.
If the cadence is shorter than the billing period (for example, daily cadence with monthly billing), each cadence window gets its own independent pool, and the invoice totals the overages from each window at month-end.
Save and preview across a few periods to confirm the depletion pattern matches expectations.

Set max_per_period to the maximum number of units that can be discounted within a single cadence window, even if value is higher.
Save and preview — usage beyond the cap within that window is billable even though the nominal pool (value) hasn’t been exhausted.

Set max_lifetime to the cumulative number of discounted units that can ever be consumed across the contract.
Remember that only units actually applied against usage count toward this cap — unused, wasted units in any given pool don’t reduce the remaining lifetime balance.
Save. Once the lifetime cap is reached, all further usage becomes billable with no further discount.

Set prorate_stub to true on the discount configuration.
Set rounding to control how a fractional prorated pool is rounded — floor rounds down (favors the business), ceil rounds up (favors the customer), or half_up for standard rounding. The default is floor.
Save. This only affects partial cadence windows, such as a contract starting mid-cycle — full cadence windows always get the full value.
Leave prorate_stub at its default (false) if you want the full pool applied even to partial windows.

Add each quantity discount to the line item with its own value and cadence.
Set the order field on each to control which pool is drawn from first.
Save and preview — usage is offset against the first discount’s pool before falling through to the next one in the configured order.

Add the quantity discount and set its order to come before the percent or fixed discount.
Add the percent or fixed discount with a later order value.
Save. The quantity discount reduces billable units first; the resulting dollar amount is then reduced by the percent or fixed discount.

Before saving, check the line item’s pricing model — if it’s volume or tiered pricing, a quantity discount changes the billable quantity used to determine the bracket, not just the final bill.
For volume pricing specifically, run the numbers both with and without the discount to confirm the resulting bracket and total — in some cases, a quantity discount can push the customer into a lower bracket with a higher rate, increasing the invoice.
For tiered pricing, this paradox doesn’t occur — fewer billable units always result in a total less than or equal to the undiscounted total.

Open the invoice and find the quantity discount line.
Each period’s breakdown record includes: quantity before and after the discount, the discount applied, the pool’s state before and after, lifetime units used, and whether any cap was hit.
Use this to verify pool depletion and cap behavior match what was configured, especially across cadence windows that span multiple billing periods.