By Kate Abnett

BRUSSELS (Reuters) -European Union companies will be required to disclose details of their Russian gas deals to the EU, under upcoming European Commission proposals to ban Russian gas imports by the end of 2027, an internal Commission document, seen by Reuters, showed.

The Commission is preparing to propose legal measures to completely halt the EU's Russian gas imports by the end of 2027, and ban new Russian gas deals by the end of this year. The proposals are due to be published on June 17.

An internal European Commission analysis of its upcoming proposals, seen by Reuters, said to enforce the ban, the Commission will require information including the duration, annual contracted volumes, destination clause and date of conclusion of their Russian gas contracts.

"The implementation of the measures - as designed in the proposal - requires comprehensive and systematic information about the existing contracts for Russian gas, including specific contractual arrangements," the document said.

Gas importers will also be required to disclose the origin of their imports, to ensure it is not Russian, the document said. The disclosures aim to ensure the EU and countries' customs and energy authorities can ensure the ban is enforced.

"Except for cases where gas can clearly be considered as of Russian origin, the proposal requires importers to present documentation to the customs authorities about the origin of the imported gas," the document said.

The Commission's assessment said the upcoming proposals will ban EU LNG terminals from providing services to Russian customers from January 1, 2026, with a longer deadline of June 17, 2026 for existing services contracts under short-term LNG supply deals.

The deadline to stop providing these services under long-term contracts with Russia will be December 31, 2027, it said.

A Commission spokesperson declined to comment on the upcoming proposals, which could still change before they are published.

(Reporting by Kate Abnett, editing by Bart Meijer and Louise Heavens)