The breakthrough in contract talks comes after a protracted negotiation with Shearer in which the 71-year-old actor declared he was walking away from the series.

Shearer's deal is reportedly the same as his co-stars: a two-year contract, covering a 27th and 28th season of the show, at a pay rate of around US$300,000 per half-hour episode.

With approximately 22 episodes per season, the deal is worth around US$13.2 million over two years to Shearer.

It is understood the contract also includes an option for a 29th and 30th season. It is the second time Shearer has been a lone holdout in contract negotiations for the hit Fox series. There was a similar standoff in 2011.

The source of Shearer's dissatisfaction, however, still remains something of a mystery.

Though the long-running animated series has traversed some contractual bumps in the road with its voice talent in the past, the show's producer Al Jean said the show was "not forcing [Shearer] out."

Shearer had indicated that he wanted the "freedom to do other work", though speaking to US media Jean noted that all of The Simpsons cast are free to do other work.

"He said he wanted to do other projects, which makes no sense because we've always let the cast do all the other projects they want, they have great free time," Jean said.

Though the series has "killed off" some characters in its near-three decade history, Jean said that was not an option in this case, even if Shearer did not return.

Had he not returned to work, the show would have recast his characters, Jean said. Jean had told US media he was genuinely perplexed by the standoff.

"I'm not trying to be argumentative but I have no idea what we're preventing him from doing," Jean said.