i.MAS / i.SAF — world's first universal SAF-T VAT register

i.MAS (Išmanioji mokesčių administravimo sistema — Smart Tax Administration System) is the tax-digitalisation programme launched by the VMI in 2014. Its i.SAF module, in force from 1 October 2016, made Lithuania the first country in the world to impose a universal SAF-T VAT report on every taxable person — 15 months before Poland (JPK), 21 months before Hungary (RTIR), 9 months before Spain (SII).

History — world's first universal SAF-T VAT

Lithuania chose very early a post-fact CTC approach (continuous transaction controls after the event) rather than a real-time B2B e-invoicing mandate. VMI deployed a suite of i.MAS modules aimed at near-real-time transactional consolidation, without making e-invoicing mandatory. This strategy — discreet yet radical — makes Lithuania the quiet pioneer of CTC in Europe.

2014       | VMI publishes the i.MAS roadmap — Išmanioji mokesčių
           | administravimo sistema (Smart Tax Administration System).
           | 6 modules planned, deployment 2014-2020.
           |
2 Jan 2014 | i.EKA — RKDS Registro kasos duomenų sistema. Lithuania
           | becomes the first EU State to mandate online integration
           | of cash registers with the tax authority.
           | 4 years before Italy SdI, Hungary RTIR, Portugal SAFT-PT.
           |
1 Oct 2015 | i.VAZ goes live. Real-time reporting of goods waybills
           | (physical movement of goods).
           |
1 Oct 2016 | i.SAF in force — EVERY Lithuanian VAT taxable person must
           | submit monthly their register of issued and received
           | invoices (XML SAF-T subset). FIRST in the world — Poland
           | JPK arrives Jan 2018, Hungary RTIR July 2018, Spain SII
           | July 2017.
           |
2017       | Mokesčių administravimo įstatymas (Tax Administration Act)
           | revised to anchor the i.SAF obligation in law.
           |
2019-2020  | i.SAF-T rollout — full SAF-T (OECD Standard Audit File
           | for Tax 2.0) on demand or annually depending on size.
           |
2021       | i.MAS ↔ e.sąskaita integration. Automatic reconciliation
           | of B2G invoices ↔ monthly VAT return.
           |
2023-2026  | API modernisation, native Smart-ID integration, ViDA
           | preparation — i.SAF will become the main rail for B2B
           | reporting post-2028.

Governance — VMI + Finansų ministerija

i.MAS is operated directly by the VMI (Valstybinė mokesčių inspekcija — State Tax Inspectorate), under the Finansų ministerija. The legal framework rests on the Mokesčių administravimo įstatymas (Tax Administration Act), revised in 2017 to anchor the i.SAF obligation.

The i.SAF spec is published on vmi.lt and inspired by the OECD SAF-T 2.0 spec (2010), but with its own schema adapted to the Lithuanian PVM register. All schema changes go through a technical committee VMI + Lietuvos buhalterių asociacija (accountants association) + ERP vendor representatives (Rivilė, Stekas, Pragma, B1.lt).

Modules — i.SAF / i.SAF-T / i.VAZ / i.EKA

• i.SAF — monthly register of issued and received invoices. SAF-T subset (SalesInvoices + PurchaseInvoices + partial MasterFiles). All PVM taxable persons, filing before the 20th of month M+1.
• i.SAF-T — full SAF-T 2.0 (journal + ledger + customers/suppliers + fixed assets). On VMI request, or annually for entities above thresholds (turnover, headcount).
• i.VAZ — real-time waybill declaration for domestic goods transport. Live since 1 October 2015.
• i.EKA / RKDS — online cash registers. All receipts flow in near-real-time to VMI since 2 January 2014. First EU mandate of its kind.
• i.APS — pre-fill module for PVM returns based on i.SAF / i.EKA / i.VAZ data.
• i.SKO — risk analysis and tax-audit selection module, fed by i.MAS streams.

<?xml version="1.0" encoding="UTF-8"?>
<iSAFFile xmlns="http://www.vmi.lt/cms/imas/isaf">
  <Header>
    <FileDescription>
      <FileVersion>iSAF1.2</FileVersion>
      <FileDateCreated>2026-06-10T08:14:00</FileDateCreated>
      <TaxEntity>VMI</TaxEntity>
      <TaxRegistrationNumber>LT100001738313</TaxRegistrationNumber>
      <SelectionCriteria>
        <SelectionStartDate>2026-05-01</SelectionStartDate>
        <SelectionEndDate>2026-05-31</SelectionEndDate>
      </SelectionCriteria>
      <RegistrationNumber>123456789</RegistrationNumber>
    </FileDescription>
  </Header>
  <MasterFiles>
    <Customers>
      <Customer>
        <RegistrationNumber>987654321</RegistrationNumber>
        <VATRegistrationNumber>LT987654321</VATRegistrationNumber>
        <Name>UAB Pavyzdys</Name>
      </Customer>
    </Customers>
  </MasterFiles>
  <SourceDocuments>
    <SalesInvoices>
      <Invoice>
        <InvoiceNo>2026/00917</InvoiceNo>
        <InvoiceDate>2026-05-21</InvoiceDate>
        <CustomerInfo>
          <RegistrationNumber>987654321</RegistrationNumber>
        </CustomerInfo>
        <DocumentTotals>
          <TaxPayable>252.00</TaxPayable>
          <NetTotal>1200.00</NetTotal>
          <GrossTotal>1452.00</GrossTotal>
        </DocumentTotals>
      </Invoice>
    </SalesInvoices>
  </SourceDocuments>
</iSAFFile>

i.SAF vs classic SAF-T vs SII vs RTIR

Adoption — universal coverage

• ~120,000 PVM taxable persons submit i.SAF monthly (VMI figure 2024).
• ~1.2 billion invoice lines processed by i.SAF every year — i.MAS is one of Europe's largest tax data warehouses relative to population (~2.8 M).
• Automatic PVM pre-fill via i.APS since 2018 — massive compliance-cost reduction for SMEs.
• Lithuania VAT gap ~14% in 2024 (CASE / European Commission) — continuously decreasing since i.MAS deployment (-10 pts between 2014 and 2024).

Common pitfalls

• Confusing i.SAF and OECD SAF-T. i.SAF is a subset (just VAT register). i.SAF-T is the full SAF-T. Requirements do not trigger for the same taxable persons or at the same frequency.
• Thinking pre-fill removes the filing. i.APS pre-fills the PVM deklaracija, but the taxable person remains responsible for final filing and corrections.
• Forgetting B2C retail invoices. i.SAF reports B2C invoices too (aggregated or detailed by type). i.EKA reports cash-register receipts — double-counting must be avoided.
• Wrong currency code. i.SAF uses ISO 4217. EUR since 2015 (Lithuania joined the euro area on 1 January 2015). Historical LTL flows must remain archived but are no longer reported in current flows.
• Europe/Vilnius timezone (EET/EEST). i.SAF / i.VAZ timestamps are in local Lithuanian time (UTC+2 winter, UTC+3 summer). An ERP pushing strict UTC sees its transactions classified to the wrong tax period.

Cross-links

• Lithuania hub — full view
• e.sąskaita — B2G 2017
• RKDS / i.EKA — online cash registers 2014
• VAT regimes
• VMI — tax authority
• ViDA Lithuania 2028
• VMI — official i.MAS portal
• Įstatymo registras — Tax Administration Act