The referendum, seen as a test for the commission (NEC) just weeks before the nation's second post-war presidential elections, underlined teething problems after a misprint on ballot papers that confused some voters.
While voting went off peacefully, the referendum was also marred by concerns over poor voter turnout and a a boycott by some opposition leaders.
"The NEC assures the voting populace that the error will in no way affect the determination of the decision of the voters to vote 'yes' or 'no'. Neither will it impact the results of the referendum," chairman James Fromayan said at a press conference late Tuesday night.
Voters were asked to vote for or against four law changes.
However when asked about raising the retirement age of the chief justice from 70 to 75, a misprint created confusion among the electorate even though it preserved the alternative of approving or rejecting the amendment.
Fromayan said while turnout had been slow in the morning, it was encouraging later in the day, amid fears many of the 1.8 million registered voters had decided to stay away.
"The commission is glad that the process unfolded in an organised manner."
Some opposition leaders refused to vote, opposing the referendum which could change the election date and candidacy requirements in the midst of campaigning for presidential and legislative elections on October 11.
The main opposition Congress for Democratic Change (CDC) candidate Winston Tubman, the Harvard-trained nephew of Liberia's longest serving president, denounced the referendum as unconstitutional.
He said it was "too close to election time, too much money wasted and too much work for the election commission".
The stickiest change proposed under the referendum will amend the length of time presidential and vice-presidential candidates must have lived in Liberia from 10 years to five consecutive years.
This clause was suspended in 2005 elections since most candidates had just recently returned from exile.
Observers say that if the change is passed, it could open up the field to more opposition parties, increasing President Ellen Johnson Sirleaf's chances of re-election.
It could also disqualify some candidates such as Reverend Kennedy Sandy, of the Liberia Transformation Party (LTP) who had lived in America since 1989, recently returning to run for office.
Football legend George Weah could also be counted out as he left to study in America after criticism he was not well-educated enough to be in office, after losing to Sirleaf in the 2005 vote. He is the CDC's vice presidential candidate.
The International Crisis Group, a Brussels-based think tank, said in a report last week that if this clause was changed "the courts would probably have to interpret its possible effect on the fast approaching election".
Another key change would shift the election date to November 8, to avoid the logistical nightmare of holding the polls in the middle of the rainy season.
The final change aims to do away with expensive run-off elections in local and legislative polls and have public officers elected in a single round.
Copyright AFP (Agence France-Presse), 2011