SPRINGFIELD, Ill. (AP) – The Illinios Commerce Commission cleared the way Wednesday for a final decision on a 6.9 percent, $60.5 million rate boost for Illinois Power Co. after dismissing last-minute questions that threatened to swell the increase to $73 million.

The panel scheduled a vote Thursday morning on a rate plan that would boost residential customers’ bills by an average of 7.9 percent and raise commercial and industrial rates by almost 6.2 percent.

The proposal, informally endorsed by a majority of the seven commissioners, gives the Decatur-based utility only a small fraction of its request for $2.55 billion in added revenue over 11 years.

Illinois Power wants the money to pay off some of its $3.8 billion investment in the Clinton nuclear power plant, but consumer groups have argued that the plant is not needed and was so plagued by construction-cost overruns that rent payers should bear none of its cost.

The ICC had been fine-tuning its rate plan for nearly a week in anticipation of a vote Thursday, but that timetable was nearly derailed Wednesday by a complicated accounting question involving federal investment tax credits for the Clinton plant.

ICC staff members and Illinois Power officials had differed on the issue during hearings in the rate case, and ICC hearing examiner William Showtis used the staff’s version in drafting a plan that was the basis for the commission’s deliberations.

But Commissioner Ruth Kretschmer, who was not present for meetings earlier this week, indicated Wednesday that U.S. Internal Revenue Service rules might force adoption of Illinois Power’s position on the tax credits, leading to a $73 million increase.