Colorado’s vote tabulation machines counted ballots accurately during this month’s midterm election, according to results from a statewide audit that took place this week.

County officials from 63 Colorado counties participated in the routine postelection process, known as a risk-limiting audit, on Monday and Tuesday. During the audit, bipartisan teams of election workers use software to blindly compare a random sample of paper ballots against results recorded by their tabulation machines.

This year’s audit found no mismatches in statewide races, the Secretary of State’s office said.

“A successful risk-limiting audit shows that a random sample of votes was counted by machines accurately and verifies the results of our elections,” said Jack Todd, a spokesman for the office, in a statement. “This is just one of the many tools Colorado uses to ensure transparency and accuracy in our elections.”

One county, San Juan, did not participate because officials hand-counted ballots.

Several counties, including Kiowa, Lincoln and Routt counties found discrepancies in at least one local race tally, which means they will have to conduct a second round of auditing. Small discrepancies are fairly common and usually the result of human error during the audit – not because a tabulation machine counted votes incorrectly.

Each discrepancy is also investigated and published in a public report once the audit is certified.

If no discrepancies are found, that’s a sign that there’s a high level of statistical confidence in the original ballot count. If too many errors are found, audit workers must pull more ballots to ensure the “risk limit” of the election being miscounted is small enough.

In Colorado’s case, the risk limit is about 3%. If additional auditing finds more errors, a full recount is triggered. That’s never happened before, according to the Secretary of State’s office.

Colorado was the first state to require this type of audit after lawmakers passed an election security law in 2009. The first audit wasn’t held until the November 2017 general election because of delays in developing the required technology.

Now, more than a dozen states either require audits or are testing them as pilot programs to help ensure election accuracy.

Many counties record and even livestream the process online to help reassure the public that their community’s election results are secure – a task many say is becoming more difficult due to the spread of misinformation about voting and a rise in the number of election deniers running for office.

“We’re not just counting ballots and hoping for the best,” said Sahari McCormick, clerk and recorder for Gilpin County. “I really think Colorado has crossed every T and dotted every I in coming up with how to handle an election.”

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