The royal commission into child sex abuse may need to have separate public and confidential volumes in order to avoid prejudicing Cardinal George Pell's legal case.

The final report is expected to be in the order of 15,000 pages long and goes to the federal government on December 15.

AAP understands the commission and government are grappling with potential legal issues over the Pell case.

The royal commission has only examined Pell's handling of abuse allegations against other clergy in the church while he was Melbourne Archbishop and a Ballarat priest and not claims against him personally.

Pell, Australia's highest-ranking Catholic official and ranked number three in the Vatican, was charged in June with multiple historical sex offence charges involving multiple complainants.

There has been speculation in legal circles that the public release of the final report and Melbourne and Ballarat case studies may have to be delayed.

It's understood that confidential volumes may be used instead, like in the royal commission on trade union corruption.

"All royal commission reports will be provided to the government in the normal way. The tabling and publication of any reports are a matter for government," a spokeswoman for the Royal Commission into Institutional Responses to Child Sexual Abuse told AAP.

It's understood the federal government has not set a date for the final report's public release and is waiting to examine material in the report before deciding.

Victorian prosecutors have until September 8 to hand over briefs of evidence to Pell's defence team.

A date for a committal hearing is expected to be set in October.