Ask a server what a dish costs and watch where they look. If the answer lives in two places, the till and the printed menu, sooner or later those places disagree, and the guest is the one who finds out. A price rings up higher than the menu promised, and a two-pound discrepancy costs you more goodwill than a comped dessert.
Two sources of truth is one too many
The usual story is not carelessness. The menu changed on a Tuesday, the till was going to be updated after service, service ran long, and by Friday nobody remembers which price is the real one. Multiply that by specials, by 86'd dishes, by the wine that came back into stock, and the drift is constant.
- Decide, once, which system is the source of truth for names and prices
- Everything else should be fed from it, not maintained alongside it
- If a change needs typing twice, it will eventually be typed once
What syncing actually buys you
A menu that feeds the till means the person who changes the halibut price at 4pm has already updated the till, the website, the QR menu and tonight's print run, because they are all the same change. It also means stock is honest in both directions: when the kitchen 86's a dish, it vanishes from the guest-facing menu instead of surviving there as a small ambush.
If your till cannot take a live feed yet, the discipline still pays. A single published menu, changed in one place at a known time each day, with the till updated from that page and not from memory, removes most of the drift. The software helps, but the habit is the point.