Wedding preparation is underway for Gwen Stefani and boyfriend of less than a year, Blake Shelton!

A source tells Life & Style that the couple will announce their engagement in September and marry in a Christmas ceremony.

MUST SEE: Gwen Stefani Almost Unrecognizable in Selfie With Boyfriend Blake Shelton — See the Pic!

“They’re planning a December wedding at Blake’s ranch in Oklahoma because Gwen and the boys love it there and it will give them a lot of privacy," the insider dishes.

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In fact, on a recent break from her concert tour, the 46-year-old blonde beauty and her three sons spent a day at the Voice coach's abode, riding ATVs and making cheese dip.

At the moment, the source says the duo is hammering out their prenuptial agreement. “The prenup will dictate that their earnings remain separate," the insider shares of the pair's combined $225 million fortune.

For more on Gwake’s relationship, pick up the latest issue of Life & Style, on newsstands now! And scroll through the gallery below for cute photos of the couple.