The three-man panel, chaired by Lord Nimmo Smith, was set to begin hearing evidence on Tuesday after the SPL began an investigation into alleged undisclosed payments to Rangers players from 2000 to 2011.
The probe was launched before the original Rangers company was consigned to liquidation and the newco club have refused to recognise or co-operate with the investigation. At the weekend, Rangers called for the investigation to be halted and warned that the ultimate sanction of title-stripping could see fans refuse to attend away games in future.
But on Monday night Doncaster said: "The independent commission will start tomorrow, as has already been planned. There were allegations that a number of SPL rules were broken over a number of years.
"Those allegations are complicated and are serious. It's for an independent commission to take forward these complex issues and decide whether any SPL rules were in fact broken and, if indeed they were, to decide on any sanction.
"But it's an independent process and that independent process will start tomorrow. I'm not going to predict when there might be an outcome."
The payments centre on financial arrangements made by the Employee Benefit Trust scheme run by former Rangers owner Sir David Murray's company.
Murray International Holdings won its appeal in principle against a tax bill surrounding the EBTs, with most of the payments deemed to be loans. Her Majesty's Revenue and Customs launched an appeal against the verdict.
The SPL charge relates to rules that say all payments to players for football activities must be stipulated in contracts registered with the league.