COLUMBIA -- More than 74,000 people who skipped voting in past elections may have been excluded from data used to estimate how many voters lack state-issued identification that is at the heart of South Carolina's new law requiring photo IDs to vote, the State Election Commission said Friday.

Under the new law, people have to present photographic identification at precinct polling places to cast regular ballots. The data crunching is important because it will be used to reach out to voters to make sure they know about the change, an issue the U.S. Justice Department is concerned about as it reviews the law.

There is enough question about the data that the state on Friday delayed filing responses to the U.S. Justice Department's questions about the new voter ID law, Deputy Attorney General Bryan Stirling said.

The Election Commission said this week that nearly 217,000 registered voters in the state lack a state driver's license or photo ID. That already was nearly 40,000 more than the election agency had previously estimated.

Election Commission spokesman Chris Whitmire said data used to match state driver's license and identification card data excluded about 117,000 inactive voters. That figure includes a mix of people who had died, moved, been convicted of crimes that suspend their voting rights or hadn't voted since 2006.

The state marked 74,511 voters as inactive in 2009 because they hadn't voted in general elections in 2006 or 2008. Whitmire didn't have an estimate of how many of those voters subsequently became active because they voted in the 2010 election.

Meanwhile, the state Department of Motor Vehicles said Friday that its data excluded people who didn't renew driver's licenses or state ID cards on their birthdays. The agency said it had no way of estimating how many of the 4 million holding those credentials missed renewal deadlines when the snapshot of drivers and ID card holders was made.

South Carolina's past voting-law abuses mean the Justice Department must approve election-law changes under the 1965 Voting Rights Act.

The Justice Department already has asked about how the state will educate voters on the new law, and how many people may lack identification. It specifically asked for information on registered voters.

The Election Commission told state attorney general's office on Sept. 13 that the data it was collecting would show "a list of registered voters and demographic statistics of those voters."