All subjects of the Accounting Law registered in Latvia. No single mandatory transport channel: eAdrese, Peppol access points and other mutually agreed methods are all acceptable (email is permitted but officially discouraged). B2C is out of scope.
Latvia is the correction case: a great many trackers still show 1 Jan 2026 for Latvian B2B. That date was killed by the 5 June 2025 Accounting Law amendments and moved to 1 Jan 2028. The Budget and Finance Committee explicitly rejected a 2027 compromise. What DID start in January 2026 is the VID data-reporting duty on the B2G side only.
3 of 4 are primary sources. Mandate dates move — treat this page as a starting point and confirm against the primary source before committing a plan.
A page is a starting point. A scoped analysis gives you the specification, the mapping and the effort — in weeks, not quarters.