To replace a real cash register in the EU (Dutch tax rules, 7-year retention), the POS/invoicing needs:
  1. An audit trail: every sale and every correction logged with continuous numbering, nothing silently overwritten.
  2. A daily Z-report / end-of-day: revenue per payment method (cash, card/PIN, iDEAL, bank transfer) and per VAT rate (21/9/0).
  3. Cash drawer management: opening balance, cash in/out, counted cash and difference.
  4. Export of these reports (PDF/CSV) per day/month for the accountant.
Without this, small clinics and shops must keep a separate till next to HighLevel.