I.MAS will consist of 7 subsystems:
1. Smart cash register subsystem (i.EKA) – taxpayers will be obliged to provide information to the tax authority on cash desk operations remotely in real time or at the determined time intervals.
2. Electronic invoicing subsystem (i.SAF) – taxpayers, issuing invoices, will be obliged to file data on received and issued invoices using software in standardised data format by electronic means to a tax administrator.
3. Electronic consignment note subsystem (i.VAZ) – mandatory issue of a consignment note entitling to transport freight in the territory of the Republic of Lithuania. Taxpayers will issue, transfer, receive and use electronic consignment notes. Moreover orders will be formed, transferred and received using the subsystem for freight transportation by road transport.
4. Subsystem of remote accounting services for small businesses (i.APS) – allowing self-employed persons and small businesses to manage income–expenditure accounting by electronic means, using data accumulated in other i.MAS subsystems.
5. Subsystem of standard accounting data accumulation and management (i.SAF-T) – taxpayers will be obliged to export accounting data from the accounting systems in a standard audit file and submit it to the tax authority.
6. Permanent taxpayers’ control subsystem (i.KON) – creates conditions to observe everyday economic operations of taxpayers and organise efficient actions to ensure the identification and management of tax evasion risks. In a real time or with a few days delay the tax administrator will be able to track information on cash operations and movements of goods at a level of an economic operations, also execute a control of a content of VAT returns filed by taxpayers and inform efficiently taxpayers regarding nonconformities identified.
7. Subsystem of analysis, modelling and risk management (i.MAMC) – enables the usage of information collected from various sources for the purpose of behavioural analysis of tax payers and assessment of the impact of control actions.

It is planned to implement e-invoice (i.SAF) and e-consignment (i.VAZ) subsystems by October 2016.

Profit-seeking taxpayers must be prepared to file accounting document data in the standard accounting data file (i.SAF-T):
• From 1 January 2017, if net sales revenue exceeds EUR 8 million in financial year 2015;
• From 1 January 2018, if net sales revenue exceeds EUR 700 000 in financial year 2016;
• From 1 January 2019, if net sales revenue exceeds EUR 45 000 in financial year 2017;
• From 1 January 2020 and later years, if net sales revenue exceeds EUR 45 000 in the previous financial year.