Lithuania’s Smart Tax Administration System, i.MAS (Išmanioji mokesčių administravimo sistema), has been the backbone of the country’s digital tax control since 2016. A decade on, it is no longer a future project: it is the daily reporting infrastructure that every VAT-registered company in Lithuania, including foreign-owned subsidiaries and branches, must work with. In 2026 and heading into 2027, i.MAS is also entering a new phase, as Lithuania moves further toward real-time, data-based tax administration in line with EU-wide digital reporting reforms.
What i.MAS Actually Requires Today
Run by the State Tax Inspectorate (VMI), i.MAS today consists of several modules, but three are directly relevant to most foreign businesses operating in Lithuania:
- i.SAF – the electronic VAT invoice register. Every VAT-registered business, including foreign companies with a Lithuanian VAT number, must submit data on issued and received invoices monthly, by the 20th day of the following month, alongside the VAT return. Importantly, these obligations apply not only to Lithuanian entities but also to foreign businesses registered for VAT in Lithuania, even where they do not have a permanent establishment in the country.
- i.VAZ –the electronic consignment note subsystem, mandatory for the domestic transport of goods by road within Lithuania. While i.VAZ does not cover all cross-border movements of goods, it may apply where goods are transported domestically within Lithuania, making it important for foreign businesses to assess their logistics flows and reporting obligations carefully.
- i.SAF-T –the standardised accounting data file. Unlike i.SAF, this is not a routine monthly filing. Instead, VMI may request it at any time, most commonly during a tax audit, and the company must be able to provide it within the specified deadline. In practice, businesses should not wait until a request is received. Accounting systems should be capable of generating a compliant SAF-T file at any time, as preparing the file can be challenging if data quality and system configurations have not been tested in advance.
Other modules, such as i.EKA (smart cash registers), i.APS (simplified accounting for sole proprietors) and i.KON (continuous risk monitoring), operate largely in the background or target specific taxpayer groups. However, they all feed into the same VMI data ecosystem, which automatically cross-checks invoice, VAT return and other transaction data. Together, these systems provide VMI with a detailed view of taxpayers’ activities and enable increasingly automated risk assessments, anomaly detection and audit selection.
Why This Still Matters for Foreign Companies
For a foreign investor, i.MAS is not optional paperwork: VMI’s systems flag mismatches between i.SAF data and VAT returns automatically, and discrepancies routinely trigger inquiries or audits without any manual review on the tax authority’s side. Non-compliance carries real financial exposure. Failing to submit i.SAF, submitting it late, or filing inaccurate data can result in penalties ranging from roughly EUR 200 up to EUR 6,000, depending on the severity and whether the violation is repeated, on top of daily late-payment interest on any underpaid VAT, calculated at the rate applicable at the relevant time.
In practice, this means accounting systems, invoicing software and internal processes all need to be capable of producing i.MAS-compliant data, not just correct bookkeeping in the traditional sense. For foreign businesses, ensuring that ERP systems, tax codes and invoice data are correctly configured for Lithuanian reporting requirements can significantly reduce the risk of reporting errors and subsequent tax authority inquiries.
What Is Changing in 2026 and 2027
Two developments are worth tracking closely over the next two years:
- SABIS migration. Business-to-government (B2G) e-invoicing, previously handled through the e.sąskaita portal, has been migrating to the new centralised platform SABIS (Sąskaitų administravimo bendroji informacinė sistema), which is now operating at full capacity. Companies that invoice Lithuanian public sector clients should confirm their invoicing software or service provider is aligned with SABIS.
- Direction toward mandatory B2B e-invoicing. Lithuania is developing a structured business-to-business e-invoicing framework intended to converge with the EU’s ViDA (VAT in the Digital Age) initiative. While full mandatory B2B e-invoicing is not yet in force, the direction of travel is clear, and businesses that build ViDA-ready invoicing capacity now will face a smaller transition later.
Alongside these system changes, businesses should also keep an eye on VAT rate mechanics: since 2026, Lithuania’s VAT return (FR0600) includes a dedicated field for domestic services taxed at the new 12 percent rate, following the abolition of the former 9 percent reduced rate. Getting the rate and the corresponding i.SAF entries wrong is one of the more common compliance errors we see.
How Leinonen Can Help
Leinonen Lithuania’s accounting and tax teams work with i.MAS reporting daily on behalf of foreign-owned clients. We can review whether your current accounting or invoicing setup is i.MAS and SABIS-ready, handle your monthly i.SAF and i.VAZ submissions, prepare i.SAF-T data ahead of an audit request, and help you plan for the upcoming shift toward mandatory B2B e-invoicing. If you have questions about your reporting obligations in Lithuania, please do not hesitate to contact Leinonen Lithuania’s tax and accounting team.
