During all of these discussions about the budget crisis in Alaska, Walker and the legislature have allowed the oil companies to go unaudited.  

The few audits that were completed should have brought the state $488 Million but the state is not bothering to collect on it.

"The first wave of net tax audits from 2006 and 2007— completed from five to nearly six years later — resulted in $488 million in additional tax assessments. But whether the money will be collected "is unknown at this time"

The statute of limitations is running out on these audits, but if they were completed, the state stands to gain billions. See "Statute of limitations running out on state oil tax audits, report warns"