The 'Bodies' hitmaker - who left the group in 1995 following a rift with his bandmates - has reportedly agreed to perform with Gary Barlow, Howard Donald, Jason Orange and Mark Owen for the first time in 15 years for British charity Children In Need.
A source told Britain's The Sun newspaper: "The reunion is go. Robbie is utterly thrilled about it. He's been dreaming of performing with Take That again for years and now it's going to happen.
"Gary is looking forward to singing with Rob again, but landing Paul McCartney is without doubt his biggest coup. They haven't decided what they are going to sing together, but something will take shape in rehearsals."
Robbie - who has previously battled alcohol and drug addictions - walked out on the band in 1995 and famously refused to speak to bandmate Gary for 10 years.
But in 2005 the pair made contact and have since been writing together.
Meanwhile, Take That bandmate Mark got his sister to sing at his wedding.
The pintsized star asked Tracy to perform with a choir when he tied the knot last weekend to Emma Ferguson, and she wowed the congregation with a rendition of Judy Collins' version of Amazing Grace
A source at the service said of Tracy's performance: "She was amazing. Singing definitely runs in the family."