The NSW Electoral Commission says its iVote registration system is down and is pleading for patience.

People who have a disability, are sick or are outside of NSW on election day, have until 1pm on Saturday to register for iVote and until 6pm to cast their vote via the website or over the phone.

"The problem relating to online registrations has resulted in increased call volumes to our call centre," Commissioner John Schmidt said.

"Our call centre is still processing registrations, however some people have been reaching a pre-recorded message asking them to call back later. This is due to the high volume of calls."