RKDS / i.EKA — first EU mandate of online cash registers
The RKDS (Registro kasos duomenų sistema — Cash Register Data System) came into force on 2 January 2014. That day, Lithuania became the first EU State to mandate near-real-time integration of cash registers with the tax authority. Italy (SdI) follows 4 years later, Hungary (RTIR) also, Portugal (SAFT-PT real-time) 5 years later. It is the founding act of Lithuanian post-fact CTC.
History — EU first on 2 January 2014
VMI laid RKDS as the first pillar of i.MAS in 2010, in an 18-month pilot phase. The universal mandate entered force on 2 January 2014, anchored in the Mokesčių administravimo įstatymas and a related Vyriausybės nutarimas (government resolution). The schedule places Lithuania as world pioneer, even ahead of Italy's early SdI experiments (B2G 2014, B2B 2019).
2010-2013 | Pilot phase — VMI develops RKDS (Registro kasos duomenų
| sistema). Reporting protocol spec published 2013.
| Mandatory hardware certification.
|
2 Jan 2014 | Universal mandate — every merchant equipped with cash
| registers must report in near-real-time their receipts
| to VMI via RKDS. FIRST EU mandate of its kind. Framework
| Mokesčių administravimo įstatymas + ancillary Vyriausybės
| nutarimas.
|
2015 | i.MAS rebrand — RKDS becomes the i.EKA module of i.MAS
| (Elektroninių kasos aparatų — electronic cash registers).
|
2017 | Protocol modernisation — switch to JSON + HTTPS, gradual
| abandonment of legacy GPRS connections.
|
2018 | Italy: launches real-time SdI for B2B (1 Jan 2019) — 4
| years after Lithuania. Hungary RTIR (1 Jul 2018): 4
| years after. Portugal SAFT-PT real-time: 5 years after.
|
2019-2021 | Cross-integration with i.SAF — automatic reconciliation
| of cash receipts ↔ monthly VAT register. Anomaly
| detection in near-real-time.
|
2023-2026 | AI modernisation — fraud detection by patterns (receipt
| deletion, cash / bank discrepancies). Preparing alignment
| with ViDA 2028.Governance — VMI + hardware certification
RKDS is operated directly by VMI. Governance has two strands: (1) the protocol specification (published on vmi.lt, annually refreshed), and (2) hardware certification — only cash registers on the VMI list may be used commercially. The list counts ~40 certified models (local manufacturers + ELCOM, Datecs, Posnet, etc.).
Protocol changes go through consultation with: Lietuvos prekybos įmonių asociacija (LPĮA — retailers association), Lietuvos viešbučių ir restoranų asociacija (LVRA — hotels-restaurants), and hardware manufacturers.
Schema — certified register → RKDS → i.MAS
┌─────────────────────────────────────────────────────────────────┐
│ Lifecycle of a cash receipt — RKDS / i.EKA │
├─────────────────────────────────────────────────────────────────┤
│ │
│ 1. Customer pays at the till │
│ │ │
│ ▼ │
│ 2. VMI-certified cash register prints receipt │
│ │ + cryptographically signs │
│ │ + generates hash │
│ ▼ │
│ 3. Register pushes via HTTPS + JSON to RKDS │
│ ┌─────────────────────────────────────────┐ │
│ │ POST /rkds/transactions │ │
│ │ { │ │
│ │ "registerId": "RKM-12345", │ │
│ │ "merchantId": "123456789", │ │
│ │ "timestamp": "2026-06-15T14:32:11+03:00", │ │
│ │ "items": [...], │ │
│ │ "totalNet": 24.79, │ │
│ │ "totalVat": 5.21, │ │
│ │ "totalGross": 30.00, │ │
│ │ "signature": "...", │ │
│ │ "hash": "sha256:..." │ │
│ │ } │ │
│ └─────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ 4. VMI / RKDS validates, stores, acknowledges │
│ │ │
│ ▼ │
│ 5. Cross-check with i.SAF (monthly VAT register) + i.APS │
│ (PVM return pre-fill) │
│ │
└─────────────────────────────────────────────────────────────────┘RKDS vs SdI vs RTIR vs SAFT-PT real-time
| System | Country | Launch | Scope | Latency |
|---|---|---|---|---|
| RKDS / i.EKA | Lithuania | 2 Jan 2014 | B2C retail registers | Near-real-time |
| SdI B2G | Italy | 6 Jun 2014 | B2G only | Real time |
| RTIR | Hungary | 1 Jul 2018 | B2B invoices >HUF 100K | Real time (24h) |
| SAFT-PT (monthly) | Portugal | 2008 | All taxable persons | M+25 |
| SAFT-PT (real-time) | Portugal | 2019 | Certified cash registers | M+5 then real-time |
| SdI B2B | Italy | 1 Jan 2019 | All B2B/B2C | Real time |
| SII | Spain | 1 Jul 2017 | Large taxable persons | 4 working days |
Adoption — national retail coverage
- ~80,000 cash registers connected to RKDS in 2024 (VMI figure).
- ~600M receipts/year reported in near-real-time to VMI.
- B2C retail VAT-fraud reduction estimated at -30% in 5 years per the 2022 VMI report — on the B2C retail segment.
- i.SAF cross-check: RKDS receipts are automatically consolidated into the monthly i.SAF B2C-sales register, sparing SMEs double-entry.
Common pitfalls
- Non-certified cash register. A register bought outside the certified list is forbidden. The offence is sanctioned by fine + confiscation. Foreign chains must check compatibility of their SAP / Oracle Retail equipment before installation.
- Intermittent connectivity. RKDS tolerates white zones (mobile retail, fairs) — the register stores and syncs as soon as connectivity returns. But a prolonged outage >72h triggers a VMI alert.
- Receipt deletion. Any deletion leaves a hash trace in the signed chain. "Phantom cash register" frauds are detected in near-real-time by i.SKO.
- Gift cards and credit notes. Must be traced with specific code (credit note = UNCL code 381). Wrong coding disrupts the monthly i.SAF consolidation.
- Confusing RKDS and i.SAF. RKDS = real-time cash receipts (B2C). i.SAF = monthly VAT register (B2B + B2C consolidated). The two coexist and cross-check.