> ## Documentation Index > Fetch the complete documentation index at: https://zenskar.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Quantity discount **Scope:** PIT and POT, all quantity strategies. ## The five configuration decisions | # | Question | Status | Notes | | - | ------------------------------------------ | ------------- | ---------------------------------------------------------------------------------------------------------------------- | | 1 | How many discounted units? | Available | e.g., 1,000 discounted API calls | | 2 | How often are they refreshed? | Available | Monthly, daily, quarterly | | 3 | What happens to unused units? | Not available | Always use-it-or-lose-it currently | | 4 | When do you pay for overages? | Available | Prepaid or postpaid | | 5 | When do discounted units become available? | Available | The discount has its own date range, constrained to a sub-range of the line item's duration; it can't extend beyond it | ## Configuration fields | Field | Description | Required | Default | | -------------- | ----------------------------------------------------- | -------- | ----------------- | | `value` | Discounted units per cadence cycle | Yes | N/A | | `cadence` | Refresh frequency (P1M, P1D, P3M, etc.) | No | None (per-period) | | `prorate_stub` | Reduce pool for partial cadence windows | No | false | | `rounding` | Rounding for prorated pool (`floor`/`ceil`/`half_up`) | No | `floor` | | `label` | Display label on invoice | No | N/A | | `order` | Execution order when stacking multiple discounts | No | N/A | ## Core calculation 1. **Pool created**: fresh pool of `value` discounted units at each cadence boundary. 2. **Deplete chronologically**: periods within the cadence window consume from the pool in order. 3. **Bill the remainder**: usage beyond the pool is billable. Resolution formula: `discounted_units = min(period_usage, remaining_pool)`. ## Cadence behavior | Relationship | Example | Behavior | | --------------------------- | ------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- | | Cadence = billing period | Monthly cadence, monthly bill | Each billing period gets its own pool | | Cadence > billing period | Quarterly cadence, monthly bill | Single pool shared across months; depletes chronologically | | Cadence \< billing period | Daily cadence, monthly bill | Each day gets its own pool; month-end is the sum of daily overages | | No cadence (`cadence=None`) | N/A | Functionally the same as cadence = billing period: each billing period gets `value` discounted units, but `prorate_stub` doesn't apply | ## Proration | Scenario | Proration? | | ---------------------------------- | -------------------------------------------- | | Contract starts or ends mid-window | Yes, if `prorate_stub=true` | | `prorate_stub=false` (default) | No, full pool for partial windows | | Full cadence window | No, full pool | | `cadence=None` | Not applicable, no cadence window to prorate | ``` pool = value × (window_days / full_cadence_days) 1,000 discounted/month, contract starts Jan 15 (17 of 31 days): Prorated pool = 1,000 × (17/31) = 548.39 ``` | Rounding | 548.39 → | Use case | | --------- | -------- | ------------------- | | `floor` | 548 | Favors the business | | `ceil` | 549 | Favors the customer | | `half_up` | 548 | Standard rounding | For POT, pricing proration operates on the dollar amount for a partial period, while discount proration (`prorate_stub`) operates on the quantity pool. These are different axes and aren't expected to interact. ## Discount stacking Multiple discounts coexist via the `order` field. Quantity discounts reduce units first; dollar and percent discounts apply to the resulting amount afterward. ``` 50 discounted (order=1) + 20% off (order=2), 200 calls @ $0.01 Step 1: 200 − 50 = 150 billable units Step 2: 150 × $0.01 = $1.50 Step 3: $1.50 × 80% = $1.20 ``` ## Interaction with pricing models | Model | Quantity discount applicable? | Notes | | ------------------- | ----------------------------- | ------------------------------------------------------------------------------------------- | | Per-unit (linear) | Yes | Straightforward: discount reduces units, remainder priced at flat rate | | Volume (non-linear) | Yes | Discounted units can shift which bracket the customer lands in, sometimes raising the total | | Tiered (non-linear) | Yes | Fewer units fill fewer tiers; total is always less than or equal to without the discount | | Package | Yes | Fewer units means fewer packages | | Flat fee | No | Fixed amount regardless of quantity | | Percent | No | Based on monetary input, not units | | Step | Yes | Fewer units means fewer steps triggered | ## Invoice presentation ``` API Calls (Jan 1–31, 2026) Usage: 3,500 calls Quantity Discount: −1,000 calls (First 1,000 discounted) Billable: 2,500 calls Rate: $0.001/call Amount: $2.50 ``` Each period produces a breakdown record with: quantity before and after discount, discount applied, and pool before and after. ## Risks and edge cases | Scenario | Handling | | ------------------------------------------- | ------------------------------------------------------------------ | | Cadence > billing period = budget depletion | "500/quarter" depletes across 3 months, not 500/month | | Discount order | Quantity discounts reduce units first, then dollar discounts apply | ## Glossary | Term | Definition | | ----------------- | ---------------------------------------------------------------------------- | | Quantity discount | Discounted units that offset billable consumption or allocation | | Pool | Discounted units available within a cadence window; depletes chronologically | | Cadence | Refresh frequency for the pool (daily, monthly, quarterly) | | Cadence window | Time span covered by one pool instance | | Prorate stub | Proportional pool reduction for partial cadence windows | | Rounding | How a prorated (fractional) pool resolves to a usable unit count | | Discount stacking | Multiple discounts on one product, ordered by the `order` field | | Breakdown | Per-period audit record: pool state, discount applied | ## Out of scope / deferred | Feature | Description | | ----------------------- | --------------------------------------------------------------------------- | | Carryover | `percentage`, `all`, `fixed` strategies with `max_balance` caps | | Expiry models | `end_of_grant_period`, `end_of_billing_period`, `end_of_contract`, `custom` | | Grant timing | `on_purchase`/`on_payment` triggers; `delay` for trials | | Per-event scope | `scope="per_event"`, e.g. "5 discounted per purchase" | | Prepaid entitlements | Grant records, dashboard balance, real-time tracking | | Batch-based expiry | Independent batches with FIFO consumption | | Faucet-and-bucket | Separate grant cadence from expiry boundary | | Cross-product discounts | Shared pool across multiple products |