LOS ANGELES – Brian Castano and Jermell Charlo will pay plenty for the second time in less than 10 months for the opportunity to become boxing’s first fully unified 154-pound champion of the four-belt era.

BoxingScene.com has confirmed that Castano will pay 12 percent of his purse – three percent apiece to the IBF, WBA, WBC and WBO – in sanctioning fees for their immediate rematch Saturday night at Dignity Health Sports Park in Carson, California (Showtime; 9 p.m. ET; 6 p.m. PT). Charlo will pay slightly less, 11 percent of his purse, because the IBF will take less from him, two percent, due to the fact that he holds its junior middleweight title and is a unified champion.

The WBO has the same rule in its bylaws, but Castano isn’t a unified champion, as he owns only the WBO junior middleweight title. In addition to the IBF belt, Charlo holds the WBA and WBC super welterweight titles.

Castano, 32, and Charlo, 31, previously paid 12 percent and 11 percent in sanctioning fees, respectively, for their controversial 12-round split draw last July 17 at AT&T Center in San Antonio.

Purses for Buenos Aires’ Castano (17-0-2, 12 KOs) and Houston’s Charlo (34-1-1, 18 KOs) haven’t been disclosed. Contracts submitted to state and tribal commissions before bouts in the United States sometimes don’t reflect the total compensation paid to boxers in high-profile, televised bouts.

Josh Taylor paid slightly less in sanctioning fees than Charlo and Castano for his first fight after becoming boxing’s second undisputed 140-pound champion of the four-belt era.

The IBF, WBA, WBC and WBO took a total of 10 percent in sanctioning fees from Scotland’s Taylor (19-0, 13 KOs) for his 12-round, split-decision defeat of English southpaw Jack Catterall (26-1, 13 KOs) in their 140-pound title fight February 26 at The OVO Hydro in Glasgow. The IBF and WBO lowered its sanctioning fees from three percent to two percent for Taylor because he is a unified champion who owns the IBF and WBO belts.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.