He didn't tell his wife, Kate, who was on maternity leave with the couple's second child and was suffering from post-natal depression.
"I think Craig tried to protect me from the direness of the situation," Kate explains.
But it turned a financial crisis into a crisis in their relationship, too. Inevitably Kate found out, and was angry he hadn't told her. She let the anger build until she almost walked out.
"We didn't communicate, and that was why it went on," she says today.
Auckland University psychologist Dr Nickola Overall says constant and honest communication is the single biggest factor in a successful modern relationship.
"If I only had one sentence, I'd say honesty is always going to be the best policy, as long as it's delivered in a good way," she says.
"Even very direct and angry and hostile communication can be really good for relationships. Usually it generates improvement in the relationship. It ensures that the couple are engaged, whereas loyal behaviour and protective buffering, and even suppressing your emotions and fears, reduces the degree to which the couple can understand each other."
A comfortable marriage
"Comfortable" is a word both Craig, 42, and Kate, 41, use to describe their marriage before the recession hit.
They met 20 years ago, when Craig was in a sales job and Kate was in her first year of nursing. It was the first serious relationship for both, and Craig asked Kate to marry him three months after they started going out.
"I found Kate easy to talk to, made me feel comfortable, easy to get to know, a nice person," he explains.
"It completely freaked my family out and all my friends out, I think, but I just had a really good feeling about it," says Kate.
Soon after they got engaged, Kate's flatmate moved out and Craig moved in. To her surprise, Kate "found it really difficult to be in close proximity to someone who wanted to be around me all the time".
"It sounds really strange but, being someone who quite likes my own space, I found it quite intrusive," she recalls. "But that didn't last very long, I got used to it and I came to enjoy it."
They had a modest wedding. Kate took Craig's surname. Craig left the decision to her.
"I actually did have that little debate with myself: am I going to change my name, is that the modern woman thing to do?" she says.
"Logically I thought about it like this: Craig has an older sister and no other siblings, I have two young brothers. I thought there's plenty of people there to carry on my family name, but in Craig's family there's just him. So I kind of did it for his family, for his dad particularly."
They shared common values such as equality and non-materialism - values common to all seven couples who were recruited for this series from the Herald's reader panel and Facebook page.
"Neither of us believes in pushing our children to succeed - we're not big on pushing academic success, we're not big on pushing sporting success," Kate says. "I think we'd both rather our children were kind and honest and good people than outrageously successful."
When they met, Craig couldn't cook. "I never learned to cook when I was at home," he says. "My dad was a person who would go to work and come home and sit, and mum would do pretty much all the housework and the cooking."
But Craig and Kate shared the chores, just as they pooled their money.
"I did teach him to cook, and I taught him some basics of laundry management," Kate laughs.
"But really it's not hard to do housework and pretty much we would say, 'Okay, I'll do the vacuuming, you mop the floors, and I'll do the laundry and you clean the kitchen, and we just sort of did it."
They share the cooking 50/50 even though she took a break from nursing last June and now works at home proofreading medical notes.
"I'm often still working when Craig gets home from work so he'll often do dinner just simply because I've got files to finish," she says.
"On the weekend probably I cook more often, but coming into summer we divvy it up - Craig's on the barbecue and I make a salad and that's that, that's dinner.
"Craig has absolutely no concerns about it, he doesn't consider anything to be beneath him as a man, and I'm just as likely to be outside on the lawnmower and I'll be helping him fix the roof."
Their weekends are "pretty much sacrosanct as a family" with daughter Sophie, now 8, and son Riley, 5.
"We tend not to do too much outside our family group," says Kate.
"And Craig and I as a couple have always spent a lot of time together. I know that friends of mine have found that stifling in their relationships, they need time alone or they need time apart or whatever. I've never really felt that, once I got over my initial shock."
Nightmare years
So when Craig's business foundered in 2008, the impact on the relationship was unexpected. They had only recently moved from Te Atatu to buy their home up in the Titirangi bush, and they had a big mortgage and two children under 3.
At first, Craig thought he could ride it out. The business never completely dried up, but orders became sporadic. He started looking for a job instead, but couldn't get one for nine months. He borrowed money from his mother.
"We took a mortgage holiday," says Kate. "If it had taken Craig one month longer to find work, we would have been out of the house."
She went back nursing a year after Riley was born, putting the children into daycare so Craig could keep working on the business and look for a job.
At the worst point at Christmas 2008, burglars stole a laptop containing all the photos of Riley's first year.
"I was just devastated," Kate says. "It was just awful, a horrible feeling, and because I was depressed at the time and my depression started to manifest itself in really weird anxiety, I started doing things like getting up at 1am and walking round the house making sure that all the windows were shut, things like that. It definitely wasn't normal behaviour."
She was put on antidepressants and went to a counsellor, which helped. Then Craig got a job.
But then the nightmare's second chapter started: Inland Revenue wanted its tax money.
"I tried to arrange an arrangement to pay it back," says Craig. "But the papers in the file kept getting lost and they said, 'You filled in the wrong forms.' I'd fill something else in, send it back, they lost it - it went on for nearly two years."
Meanwhile, interest and penalties were piling up.
"I basically wasn't coping. It was constant anxiety. I used to be scared of the postman."
Kate says: "I was angry with him for not telling me how bad things were and for not telling me what he'd been doing to keep us afloat. I didn't realise he had been using tax money to pay the mortgage and stuff like that. And so when I found that out I said, 'We should have talked about this, it was a major decision in our life.' There was anger about that, and a bit of trust was lost."
Craig took it: "I wasn't feeling good about anything at that time, that just felt like one more thing on the pile."
Kate says: "I didn't talk about it with him for a long time. I was angry and he didn't know why.
"It's a funny thing in a relationship, you literally want your partner to be able to read your mind, and yet they can't. So Craig and I had been together for so many years and I couldn't believe that he didn't understand why I was angry, but he can't read my mind, and emotions are complex things, and you do need to actually speak about them for your partner to understand where you're coming from."
It took two or three years, but finally one night the dam broke.
"I remember the night," Kate says. "I just couldn't stop. I literally think I might have shouted for, I don't know, an hour plus. It certainly felt like it. I think Craig just sat there and just took it. The kids were asleep at the time, I'm not sure how much they heard, it's not something I'm particularly proud of.
"But in many ways it just needed to happen, it's testament to the fact that I had held so much in for so long that it all came out in such an ugly, boiling rush. And when it was out, I was able to just go, 'Phew, wow, I was really holding on to some stuff there!'
"And we had a day of soul-searching and then a long, long, it felt like a 10-hour marathon talk, and just managed to work out some stuff, and I think at some point Craig said he was sorry for everything and I said that I was sorry for everything.
"We just reached a point where we were both so tired of it, because you get so tired of being unhappy, and you have to make a choice in a relationship - you are either going to be unhappy and walk away from it, or you're going to find a way to be happy again, and I think we just both really wanted to be happy again and to be happy as a family."
Unexpected reward
Restoring trust took time, but Craig and Kate were committed to it.
"I did think, 'Gosh, if we can get through this we can literally survive anything'," says Kate. "So it was just a case of gritting our teeth and going along."
Craig finally met someone face to face at Inland Revenue who cancelled all the interest and penalties, allowing him to pay the original tax bill by adding to the mortgage.
Kate found support from her neighbours. "The friends that I made locally have become probably the best friends I've ever had, because I leaned on them so much at that time."
As the children have grown, the family have found more adventurous activities. They spend every second Sunday at Piha, where the kids do nippers lifesaving. They walk and bike the bush tracks in the Waitakeres, and have started "geocaching" - hunting for packages buried at locations marked by GPS co-ordinates.
Kate has joined the bike rides. "Craig taught me to get on a bike," she says. "I hate being on a bike, I thought no way am I going to enjoy this, but he took me out to Woodhill on a bike and I loved it."
Craig has learned to enjoy books. Kate, an avid reader, has got him from never reading to the point where the pile of books on his bedside table is as high as hers.
"I'm quite proud, I have to say, that I have brought him to books, and as a consequence both our kids now have two parents who are readers and I want both our kids to be readers as well," Kate says.
Asked what was the best time in their relationship, both say it is now.
"When you come through adversity, it gives you a greater appreciation," Kate explains.
"We came out of it and actually I'm probably happier now than I've been for the last 10 years. So it's a good place now because you get perspective. So weathering things as a couple there is actually a reward at the end, that you can look back and say, 'Oh, my life is great.' It gives you perspective."
The series
• Part 1: Dawn and Bill
• Part 2: Len and Jenny
• Part 3: Mandy and Clair
• Part 4 (Today): Craig and Kate
• Part 5: Andrew and Steven
• Part 6: Joseph and Liz
• Part 7: Lewis and Clem
