The proposals were submitted on Tuesday, the European Commission said on its website on Wednesday. It did not provide details, in keeping with its policy.
The European Union executive extended its deadline for a decision on the deal to December 20 from December 6 to assess the concessions. It is expected to seek comments from third parties.
Unipapel's offer values Spicers at an enterprise value of 200 million pounds. The sale will see DS Smith shedding a non-core business.
(Reporting by Foo Yun Chee; editing by Rex Merrifield)