# 6. EVV / Service Delivery

[← Business Requirements](index.md)

## (a) Business requirements
- **Electronic Visit Verification (EVV)** is the authoritative record that a visit actually happened, for how long, and where. The nurse **clocks in and out via the app per session**, capturing GPS coordinates and timestamps.
- An **address-match tolerance** check computes whether the nurse's GPS at check-in falls within an acceptable radius of the booking address (`evv_location_tolerance_meters`). A mismatch is **advisory** — it raises a support alert / review flag but does **not** auto-cancel; it does not silently block the visit.
- If the nurse has not checked in by a configurable threshold after the scheduled start, a **no-show / late support alert** is created and the family is notified.
- **Payout is gated on EVV completion.** A session/booking becomes payout-eligible only after EVV check-out **and** the dispute window has closed (Section 10). EVV completion is the trigger that lets the booking enter the next weekly payout batch; for a multi-session engagement, payout accrues per completed session.

## (b) Iran-specific considerations
- EVV is the core operational-trust mitigation for **unobserved in-home care** of vulnerable patients who often cannot reliably report what happened (infants, dementia, post-anesthesia) — the platform compensates for unobservability with structured proof of service.
- Releasing escrow against proof of service is also a financial-correctness requirement under the Iranian "hold then pay weekly" model — the platform must not pay a nurse for a visit that has no EVV evidence.

## (c) MVP vs DEFERRED
- **MVP:** per-session GPS check-in/out, timestamps, address-match tolerance flag, no-show alerting, payout gated on EVV completion + closed dispute window.
- **DEFERRED:** continuous geofencing during a live-in shift; supervisory tele-check-ins; family-visible live care logs; consented in-home cameras.

## (d) Supporting database entities
`visit_verifications` (per session, with check-in/out GPS, timestamps, `check_in_address_match`, status), `booking_sessions`, `support_alerts` (no-show / location-mismatch), `platform_configs` (`evv_location_tolerance_meters`).

> **Related:** Data model — [Booking & Scheduling](../data-model/05-booking-and-scheduling.md).