Self-deception is a common human trait, particularly when New Year’s resolutions roll around. Marketers know this, and are ready to turn that tendency into profit.

Gyms, for instance, sell memberships to people who ate and drank too much over Christmas, many of whom will hardly use them.

But there’s one resolution that, in the long run, could cost you more than the gym – the decision to ‘get on top of your debt problems’ by taking up a zero per cent credit card deal.

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Now, as a bank salesperson once said to me, “it’ll save you money if you use it properly” – and that’s exactly the problem, as one-third of cardholders fail to do so, according to research put out by industry super fund-owned bank ME.

Most ‘zero-interest’ deals cover a chunk of debt rolled over from another credit card account.

Do you really stick to your New Year’s resolutions? Photo: Getty

The idea is that once you’ve sobered up on 1 January, you’ll diligently set about paying down the account so that by next Christmas the debt’s all gone and you’ve paid no interest, and usually just a smallish fee for the transfer.

Yeah, right! And I won’t borrow beer money from my best mate and forget to pay it back either.

In reality, the ME survey of 2216 credit card customers found that 40 per cent had tried the zero-rate switch, but that 29 per cent of all balance transfers were not cleared before the interest-free period ended.

There are two problems faced by this group.

Firstly, most zero-rate deals treat rolled-over dollars, and newly-spent dollars differently. The new purchases usually attract a high rate of interest, and rolled-over dollars also revert to a high rate when the zero-rate period has finished.

Westpac’s 55 Day Platinum Credit Card, for instance, offers a zero rate on the rollover money for 16 months, but any new purchases accrue interest at 19.84 per cent, according to creditcardfinder.com.au.

With a deal like that, you’d want to avoid new purchases as much as possible and pay down the rollover money within 16 months.

The zero-rate dilemma

Don’t take your new card to the January sales. Photo: Getty

The paradox here, is that two-thirds of customers do manage to extract value from such products by sticking to their plans.

But what about that third who fail to pay off their balances or even go further into debt, despite their good intentions?

ME’s head of deposits and transactional banking Nic Emery says most people would assume they are from lower socio-economic groups. In fact, he says, they come from all income brackets.

“We find customers fall into a ‘plan for tomorrow’ mentality, or ‘live for today’,” he said. “Many in lower SES groups are still ‘plan for tomorrow’ people. They can scrimp and save, and even plan for unexpected costs such a medical bills. So the problem is spread across income brackets.”

If you suspect you might be one of those gym-dodging, beer-money cadging, credit card splurging people, there are other options … for the credit card problem at least.

The price of success

Rolling over debt makes sense if you don’t spend more. Photo: Getty

Taking out a personal loan commits you to regular payments, so as long as you don’t rack up new spending on the card, you’ll be more likely to pay it off.

Consolidating your debts in this way makes sense, particularly if you find a low rate for the personal loan. The big four banks currently offer personal loans at fixed rates of between 13.9 and 14.7 per cent, so while they look a lot more expensive than a zero-rate deal, you’re in effect paying to overcome your own problem with willpower.

ME’s personal loan rate is 11.99 per cent, which, unusually, is higher than its ongoing credit card rate of 9.99 per cent – and it does not offer zero-rate deals. Mr Emery comments: “We won’t offer zero per cent balance-transfers − they allow debt-laden consumers to put off changing the behaviours that created unsustainable levels of debt in the first place.”

For those with more willpower, comparison sites such as finder.com.au give you all the zero-rate deals, but you still need to do a few calculations to see which zero-rate deal works best – remembering that a high annual fee can wipe out the savings on interest. The NAB premium card, for instance, has a zero-rate on both rolled-over dollars and new-purchase dollars, for 15 months, but some of that saving is unwound by a $90 per annum fee.

Hide your card in January

Don’t take your card to the new year sales. Photo: Getty

One overwhelming piece of common sense is to do your spending before you roll over to the new card – don’t rush out with the new piece of plastic to spend money in the January sales, because those purchases will be new-purchase dollars.

Finder.com.au’s Bessie Hassan says that planning to rollover a decent chunk of Christmas money can save disciplined card users a fair bit.

She said: “If you spend $2000 on Christmas this year, put it on your credit card with an average purchase rate of 17 per cent, and planned to pay it off over the next 12 months, you could save about $144 in interest by using a card with no interest on new purchases.”

But will you? Did you go to the gym much this year? If the answer’s no, you might want to think about the personal loan instead.

Read more columns by Rob Burgess here