The Sun says United are planning to hand McTominay a double-your-money new £60,000-a-week contract.
The Scotland midfielder has had an impressive start to the season, including a stunning display in the win over rivals City on Saturday.
United want to reward the academy youngster by giving him fresh terms on his current £30,000-a-week deal.
He only signed a new contract back in January until 2023, with the promise of further bonuses if he continued to perform.
A United insider said: “It's fair to say we are delighted with how Scott has responded to signing his first big contract.
“Some players tail off but he has got his head down and justified the faith the club have shown in him.
“We have always made it clear the big money will come if the younger players perform, they don't need to be looking enviously elsewhere for it."