Nine of the 15 charges related to Day's interactions with Christchurch man Matt McFarlane.
"He's directly responsible for us going bankrupt or into liquidation, " McFarlane told the Otago Daily Times this week.
McFarlane had a business buying, renovating and on-selling houses in Christchurch.
One of his businesses, Wyn Street Holdings Ltd, was officially dissolved last month, and he also personally declared bankruptcy.
McFarlane said he met Day, who did building work for him for four years, in about 2013.
He said Day bought supplies from Bunnings on McFarlane's account without telling him. He ended up $30,000 in debt to the hardware store.
"How we found out was I got a call from a debt collector. Goods showed up on a site under my name while he [Day] was building a property.
"Once that happened the insurance company told me he wasn't a licensed building practitioner. He used another builder's name."
Court documents show Day knew the identification number of a licensed builder and used it to complete paperwork for the jobs without the builder's knowledge.
McFarlane said Day worked on more than 10 jobs for him in which he did poor work which was not up to code.
The company later had to re-do this work when it could not get signed off for building consent.
Sometimes Day would take money for work he would never do, McFarlane said.
He estimated he lost about $130,000 because of Day.
"I am 53 and he has bankrupted me. I've got three years to go until my bankruptcy is finished. I won't be able to get a house or a car.
"Because of him I've lost everything."
Day was able to deceive him and others because he was able to get people to trust him, he said.
The Ministry of Business, Innovation and Employment brought the charges against Day, saying he told two separate Christchurch property owners his building licence had expired but that he would get a licensed builder to supervise and sign off on his work.
Day instead never had his building work reviewed.
Day will be sentenced in the Christchurch District Court on September 24.
- Otago Daily Times