Burgess, who played a key role in the Rabbitohs' drought-breaking 2014 championship, signed a three-year deal last month but Australian media reported weeks later the NRL were declining to register the contract over salary cap issues.
South Sydney put an end to the speculation on Sunday, saying the governing body had rubber stamped the deal.
"The Rabbitohs are pleased to inform members that Sam Burgess’ contract has been registered by the NRL this week, meaning Sam will play in the red and green of the Rabbitohs until at least the end of the 2018 season," the club said in a statement.
"Burgess is scheduled to return for the Rabbitohs in the club’s opening fixture against the (Sydney) Roosters in March 2016."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Burgess reunites with two of his brothers at the Rabbitohs. A third brother plays for cross-town rivals Manly. Their mother Julie also calls the harbour city home.
The 27-year-old remains a cult hero in South Sydney, having led the Rabbitohs to their first title in 43 years in 2014.
He switched codes to join Bath last year and was a surprise inclusion as a centre in England's squad for the World Cup.
Despite some strong performances on the pitch, he became a focus of criticism for a failed campaign after the tournament hosts made an early exit.
(Reporting by Ian Ransom in Melbourne; Editing by Peter Rutherford)
