Lenses sold only against an eye prescription in date

The customer asks: Contact lenses and prescription spectacle lenses are sold only to a customer whose eye prescription is on file and still valid

• Verdict: Ready, with limits (5)
• Door: Check before payment · area: Till controls and approvals › Questions and details during the sale
• Recipe: Optical prescriptions and lab orders
• Sample: S42 — Optical prescriptions and lab orders (pp_opt)
• Checked: 2026-10-23 · bench

What you build

Eye prescriptions as the shop's own records (spectacles or contact lenses, the test date and Valid until, each eye's values), a mark Sold against a prescription on the lens item groups, and a service that answers the check before payment. A marked line is paid only when the sale's customer has a prescription of its kind in date; otherwise the cashier reads which line, and the day the last one ran out. The service reads two fields of a prescription (its kind and Valid until), never a lens value.

Limits

• Answered when the cashier presses Pay, not when the line is entered.
• A sale made in Desk, on the Desk POS screen or through the API is not checked.
• When the service is down, or the till is offline, the sale is paid and flagged for review.
• At most three checks per POS Profile, 10 seconds together; this app takes one per profile.
• An insurer's or vision plan's share of the payment is not part of it.

Tell the customer

Your tills sell contact lenses and prescription lenses only to a customer whose prescription is on file and in date, and say which line and why when it is not.

What next

1. Tell the customer the 5 limits above, and write them into the proposal.
2. Follow the recipe: Optical prescriptions and lab orders.
3. Copy the sample: S42 — Optical prescriptions and lab orders (pp_opt), and change it.
4. Build and test it on your sandbox (request one if you have none; what is on it).
5. Run the checks: your own tests, the kit's checks and the money kit's release gate (testing and release).
6. Release through the customer's own release gate (14. Testing and release); an app other shops install goes through the App library.

Test it with your service stopped: the till applies the answer you declared for when it is down.

Related needs

• Optical lab orders tracked in iVendNext and sent to the lab — Ready, with limits (3)
• An answer for the cashier during the sale: a message, or a seal number, a reference or a warranty card number added to the sale — Ready, with limits (3)
• A beep and a yes-or-no question when the cashier scans an item we flagged — Ready, with limits (2)
• Check a product's warranty at the till — Ready, with limits (3)

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