State-run PKN Orlen said in February it plans to buy at least a 53 percent stake in Lotos, mostly from the state.
The notification marks the start of “the most important stage” of the takeover, PKN also said.
The refiner expect Commission approval for the transaction by mid-2019.
In September oil major BP (BP.L) said a merger of the Polish refiners could restrict competition in the country.
At the end of the third quarter of 2018, PKN Orlen owned 1,774 petrol stations in Poland, BP had 542 and Lotos 488, according to data from POPiHN, a Polish organization that provides research on the local fuel market.
Reporting by Agnieszka Barteczko; editing by David Stamp