Provincial council and presidential elections are scheduled April 5. UNAMA said a voter registration drive by the country's Independent Election Commission brought in more voters.
The U.N. mission said about 30 percent of the 3,007,668 voters registered during the campaign drive are women.
IEC's campaign targeted newly eligible voters, Afghans who have relocated or moved back to the country and those who may have lost their registration cards from previous elections.
"Afghan-led and Afghan-managed elections are at the very heart of the country's political transition, and UNAMA reiterates the importance of public participation in order to ensure transparent, credible and inclusive elections," the mission said in a statement.
Next year will mark the first time power is transferred from one elected government to another in Afghanistan's history.
The IEC said, as of October, there were 26 applicants, including one female, registered for presidential elections. More than 3,000 applications, including 323 women, were registered for provincial council elections.
The IEC said the names of the candidates are confidential.