The Victorian Local Government Inspectorate instigated the charges and said the former councillor pleaded guilty to six charges at Benalla Magistrates Court on July 5.
Mr van Wersch, who unsuccessfully stood for re-election in 2020 after one term, was fined $5000, without conviction, and ordered to pay legal costs of $3500.
Completion of personal interests returns is a requirement under the Local Government Act for all councillors.
Mr van Wersch failed to submit two interest returns within the required timeframe.
The Inspectorate said he also failed to disclose a number of personal interests in five of his ordinary returns, which included companies in which he held office or a beneficial interest, as well as land interests and trust interests.
The Inspectorate initially laid 18 charges against him, but accepted a guilty plea on six rolled-up charges.
“Submitting accurate personal interests returns is vital for the transparency of local government and a way for the community to ensure that decisions are made in an impartial manner for the benefit of the community and not for personal gain,” Chief Municipal Inspector Michael Stefanovic said.
“Communities have the right to expect the highest levels of integrity from their councillors.
“It also sends a message to councillors across Victoria that submitting accurate personal interests returns is essential.”
As part of a major investigation the Inspectorate examined 4600 personal interests returns from 650 councillors at 78 councils for compliance with the requirements of the Local Government Act 1989.