The couple welcomed their first child, daughter Wyatt Isabelle Kutcher in September this year, reported E! Online.
"The wedding is in the works," a source said of the pair's future nuptials.
Rumours that the duo may have gotten married surfaced this weekend after Kunis, 31, was spotted wearing what looked like a wedding band along with her gorgeous diamond engagement ring while enjoying the Los Angeles Lakers game with Kutcher, 38.