Pennsylvania Supreme Court Says Mail-In Ballots Without Dates Should Not Be Counted

The court’s ruling directly conflicted with guidance issued in September by Leigh M. Chapman, a Democrat who is the acting secretary of the commonwealth and said ballots without a date on them should be counted as long as they are returned on time.

It was not immediately clear whether state election officials could pursue an appeal.

“We are reviewing, but the order underscores the importance of the state’s consistent guidance that voters should carefully follow all instructions on their mail ballot and double-check before returning it,” Amy Gulli, a spokeswoman for Ms. Chapman, said in an email on Tuesday night.

Voters who are concerned that they might have made an error on ballots before returning them should contact their county election board or the Pennsylvania Department of State, Ms. Gulli said.

Pennsylvania is where two of the most closely watched elections in the country will be decided next week. In the governor’s race, Josh Shapiro, the state’s Democratic attorney general, faces state Senator Doug Mastriano, the right-wing, election-denying Republican nominee. And control of the U.S. Senate could hinge on the outcome of the contest between the celebrity physician Dr. Mehmet Oz, a Republican, and Lt. Gov. John Fetterman, a Democrat.