The state Department of Transportation’s balance sheet has improved considerably since accounting scandals swept the agency a couple of years ago, according to a report by the state auditor. But the audit still found accounting problems at DOT, and some may take years to fix.

After overspending in previous years, according to auditors, DOT came back and built up a surplus of $934 million as of June 30, 2010.

That’s an improvement from the fiscal year 2008, when the auditors said DOT’s books ran the risk of showing a $435 million deficit. DOT avoided that, with auditors’ approval, by shifting around $456 million of expected future revenue onto the 2008 books.

Auditors at that time listed blistering findings against DOT. While many have been resolved, DOT continues to have problems.

In the report released Friday, auditors said DOT did not maintain some of its books adequately, a result of DOT’s failure to properly monitor them and lack of an adequate system to maintain correct figures.

DOT officials have responded that some of the problems are a result of state computer systems that don’t properly comply with transportation accounting rules. DOT staff are instead making thousands of entries manually to work around the problem, which leads to a high possibility of error, they said.

Without fixes, “errors will continue to exist for many years,” DOT officials wrote to the state auditors. They said the State Accounting Office is working “diligently” on a new computer program.

Other problems auditors found in the new audit included contractors whose certifications had lapsed, contracts that were recorded on the general ledger months late, and lack of accounting control over project balances.

In 2008 and 2009, the state auditor said that DOT had been violating the state constitution by signing contracts before it had the full amount of money for the contract on hand. The DOT may not operate like a mortgage holder who pays part of the contract up front and the rest over time as more income comes in.