To fall into a bad habit takes no effort at all -- it's the good ones that we usually have to work on developing. And when it comes to financial matters, failing to put in that work can cost us a bundle, both in the short term and the long run.

Case in point: These three mistakes could take significant amounts of cash out of your wallet in 2020. But luckily, only one of them involves a hard-to-break habit.

1. Carrying a credit card balance

Any time you charge expenses on a credit card and fail to pay the balance off in full when the bill comes, you're signing up to pay interest, and frequently at a fairly high rate. That's a bad thing -- unless, of course, you enjoy throwing money away.

Imagine you build up a $2,000 credit card balance on an account with a 20% interest rate -- whether because you spent a bit recklessly or simply because you were hit with a big unexpected expense and had no emergency fund to cover it. If it takes you a year of steadily chipping away at it to retire that debt, you'll wind up throwing away $223 in the process.

Man sitting at table holding his head


A better bet? Use your credit cards more judiciously, and only rack up charges you'll be able to pay off completely when they come due. And if it's too late for that, cut back on spending or get yourself a second job so you can pay down those balances as quickly as possible to minimize the interest that accrues against you. (Then, start working on that emergency fund, so you'll be less likely to get caught unprepared next time a large expense comes up.)

2. Not snagging your full employer 401(k) match

Many employers that offer 401(k)s for retirement savings also match employee contributions to some degree. If you're not setting aside enough money from your earnings to receive that full match, you're effectively saying no to free money.

Say, for example, that your employer will match contributions up to 3% of your salary -- a common level -- and you earn $60,000 a year. All you need to do is contribute $1,800 from your earnings, and boom -- you've got another $1,800 coming your way. That's a large chunk of cash to pass up.

But wait -- it gets worse. Imagine you miss out on that $1,800 when you're 30 years away from retirement. If your 401(k) generates an average annualized return of 7% (a totally reasonable long-term result for any stock-focused portfolio), in the long run, you're sacrificing $13,700.

The takeaway? Find out what your company's 401(k) match entails, and be sure to contribute enough to claim it fully. Then, look for opportunities to keep increasing your contributions from there. It'll take a lot more than investing 3% of your salary a year to get to a comfortable retirement -- but you'll get nowhere if you don't start somewhere.

3. Not claiming all the tax credits and deductions you can

The tax code is complicated, so you may not be well-versed on all the various credits and deductions that are available to you. But if you don't make an effort to figure out what they entail and see which ones you're entitled to, you could easily end up missing out on tax savings opportunities that will put money directly into your pocket.

The Earned Income Tax Credit, for example, is an extremely valuable option for low to moderate earners. Yet according to the IRS, one in five taxpayers who were eligible for it last year didn't claim it. That's more than 6 million people.

If you have kids, you should figure out if you qualify for the Child Tax Credit. And if you're grappling with massive student loan debt, you should see if you're eligible to deduct the interest you pay on those loans from your taxable income.

A good way to ensure that you don't miss out on lucrative tax deductions and credits is to file your return electronically. Most software will do a good job of helping you identify the tax breaks you're eligible for. File on paper, and you're more likely to miss out. On the plus side, according to the IRS, 92% of tax returns last year were filed electronically, so the vast majority of people are getting that digital help.

We could all use more money -- there's no question about it. Avoid the above mistakes, and your financial health could soon take a turn for the better.