Salim Mehajer has been hit with a fine and a legal bill after pleading guilty to failing to disclose his political donations while he was deputy mayor of the now-defunct Auburn Council.

Lawyers for the colourful property developer had indicated earlier this year that Mr Mehajer intended to fight the charges but the Local Court heard on Tuesday that he had entered a plea of guilty in writing.

Mr Mehajer sent an email at 8.54am ahead of the 9.30am sentencing hearing, the court heard.

Sophie Callan, the barrister for the NSW Electoral Commission, told the court the state's electoral funding laws were aimed at preventing corruption and undue influence.