A former Belfast lord mayor is unable to vote in Thursday's local government election due to a mix-up with her postal vote.
Alliance MLA Kate Nicholl will be overseas so made arrangements to cast her vote by post.
But the South Belfast representative said the Electoral Office informed her that due to the absence of a digital registration number, her application was denied.
Ms Nicholl said the application was initially accepted by the Electoral Office and that "many constituents had also fallen foul of the situation".
"I hand delivered my correctly filled-in forms for a postal vote to the Electoral Office, where they were checked and accepted,” she said.
"I was therefore surprised to subsequently receive a letter from the Electoral Office to state we were not approved, with the reason given being a lack of a digital registration number."
The Zimbabwe-born former mayor said it was "never made clear" that the lack of a digital registration number was an issue.
"I have now been left without the ability to vote for this week and I am aware of many constituents who are in the same situation," she said.
"It has come up on the doors many times during canvassing. Clearly the Electoral Office has questions to answer – if they can email people the number with ease, why is it needed, and why are people not provided it being left disenfranchised?"
A statement from the Electoral Office, which is headed by recently-appointed Sarah Ling, said absent vote applications were processed in accordance with the relevant legislation and that if a person registered online then they must provide a digital registration number as part of their absent vote application by the deadline.
"This is stated on our website and on the absent vote application form," the statement said.
"There is signage up at the postal vote counter where electors hand in their absent vote applications to inform that the staff can only confirm receipt of the application.
"It also provides information about the digital registration number requirements and that the staff on reception cannot confirm if one is needed or not."
