---
type: concept
tags: [parking, domain, business, pricing, revenue]
sources: []
updated: 2026-06-15
status: open
---

# Validation & Discounts

A merchant (shop, hotel, clinic) **validates** a customer's parking so they pay less or nothing —
a common revenue/retention feature that modifies what a [[parking-session]] owes.

## Model: a discount is a signed event, applied at fee time

A validation is **not** an edit to the session or a mutable "discount applied" flag — same reason
as everything else ([[threat-model]]: an operator/merchant could otherwise fake free parking). It's
recorded so the fee computation and the audit both see it:

- A **discount/validation event** references the session: `{ sessionRef, kind, value, issuedBy,
  ts }` — e.g. *2 hours free*, *€5 off*, *flat €1*, *100% off*. Appended + signed
  ([[append-only-event-chain]]).
- The [[tariff]] fee function applies eligible validations when computing what's due at the pay
  station: `due = max(0, tariff_fee − discounts)` (or time-based: subtract validated minutes before
  pricing). Pure + reproducible, like the base fee.
- The `payment` event then records gross fee, discount total, and net paid — so revenue reporting
  ([[reporting-analytics]]) can show **discount leakage** (how much was given away, by whom).

## How a validation is presented

- **Merchant terminal / portal** stamps the customer's ticket id (or plate) — issues the validation
  event for that session.
- Or a **validation code** the customer enters at the pay station.
- Either way it ties to the session by **ticket id or plate** ([[parking-session]] identity).

## Anti-abuse

Because each validation is signed and attributed (`issuedBy`), over-validation by a colluding
merchant is **visible to [[reconciliation]]** (a merchant validating far more than their footfall is
an anomaly), rather than invisible free parking.

## Open

- Validation types the site needs (free hours / fixed amount / percentage / flat rate).
- Whether merchants self-serve (portal/terminal) or the operator applies it.
- Caps (max discount, max per merchant/day).