According to the outlet's insider, the pair was first leaning towards a summer wedding but because of the coronavirus pandemic are pushing it back to the fall.
Another source said that Stefani, 50, and Shelton, 44, also want two ceremonies: one in Oklahoma and another in Los Angeles.
“Oklahoma gives the couple more privacy and the possibilities are endless for a wedding reception people will talk about for years,” the source said.
“COVID-19 has turned their world upside down, as it has with so many families,” an insider explained to the outlet in June. “Gwen knows she is blessed and wants to have the wedding as soon as social distancing guidelines are lifted.”
The two musicians have been in quarantine with Stefani's three sons Kingston, 14, Zuma, 11, and Apollo, 6.
For Shelton's birthday in June, Stefani gushed over "her best friend" in a social media post.
"Happy birthday @blakeshelton thank u for being my best friend #luckyme #june18," Stefani wrote.
The couple first met in 2014 when they were coaches on “The Voice.” The following year, after both went through a divorce, they made their relationship official.
Back in April their country song, "Nobody But You," became the No. 1 single on the Billboard Country Airplay chart. It was Stefani's first-ever country song and Shelton couldn't help but applaud his love.
"Congratulations @gwenstefani on your first country song going #1 at country radio!!! Not bad for your first try!!!!! Thank you all as well!!! #nobodybutyou," he wrote.