Source: PT Money via Flickr.

I know, I know -- talking about taxes in September is like rolling out holiday decorations in August -- you just don't do it! But when it comes to life, there are only two certainties (according to Benjamin Franklin, at least): death and taxes. And taxes don't exactly care about whether something is a faux pas.

For most Americans, taxes are something we deal with on a regular basis. Most W-2 pay stubs have federal taxes taken out on a weekly, biweekly, or monthly basis. In addition, we pay property taxes on our homes, as well as sales tax on goods we buy in retail locations in a majority of U.S. states.

Yet when it comes to being smart about income taxes, most Americans aren't earning a passing grade. Whether it owes to a general lack of interest in understanding our tax situations or the complexity of tax laws, most taxpaying citizens want nothing to do with the money that comes out of their paychecks. However, that indifferent attitude can work against us.

The secret to getting the most out of your money is ensuring that you keep and invest as much as possible while also being sure to partition enough to the IRS that there are no nasty surprises come April 15 of the following year. Regardless of the type of work you do, it means you have to be proactive, not reactive, when it comes to your tax situation. However, the type of work you do could certainly have an impact on how you approach your taxes.

The one move you should make right now
This leads us to the one move you should make now, well before tax season starts: adjusting your tax withholding to fit your personal needs.

This might sound difficult to do, but it's really not. All it takes is a few minutes of planning how much you believe you'll earn in the current year, a calculator or computer, and the follow-through to adjust your withholding status with the IRS either through quarterly estimated taxes or through your employer.

Adjusting your tax withholdings is crucial to the long-term success of both self-employed individuals (those who receive 1099s) as well as persons receiving a W-2.

Source: PT Money via Flickr.

Self-employed taxpayers, listen up!
If you're self-employed, there's a good chance you'll need to pay estimated quarterly taxes throughout the course of the year. Because self-employed people don't receive a standard paycheck that is reported to the IRS, the IRS in turn expects self-employed individuals to keep up on their projected earnings by sending in one-quarter of their estimated annual taxes in mid-April, mid-June, mid-September, and mid-January.

"When do you have to pay estimated quarterly taxes?" you ask. The IRS suggests that anyone expected to owe more than $1,000 in taxes in the current year, who had a tax liability in the prior year, or who is filing as a corporation and expects to owe more than $500 based on their current-year income file estimated quarterly taxes.

It's especially important for self-employed and upper-income individuals to keep up on their estimated payments because a significant underpayment of their estimated quarterly taxes could result in a whopper of a penalty from the IRS. According to the IRS, taxpayers can avoid a penalty if their underpayment is $1,000 or if they've paid either 1) at least 90% of their tax for the current year or 2) 100% of the tax shown on the prior year's tax form -- whichever amount is smaller. There are also a select few circumstances in which the penalty can be waived, e.g., when a failure to make a payment was caused by a natural disaster. Either way, it's no fun for self-employed people to be hit with a penalty when they could have estimated their tax liability in the first place.

Employees, that goes double for you!
But self-employed Americans aren't the only ones neglecting their taxes. Millions upon millions of W-2 wage earners aren't using their earned income optimally.

Source: via Flickr.

In 2011, according to IRS data via NPR, more than 80% of people (including self-employed people) who filed a tax return received a refund. While a refund is a welcome thing for most people -- and retailers like Wal-Mart and Target certainly count on the after-tax income boost to invigorate their own sales -- getting money back from the government means you're making one of the worst tax mistakes you can make.

On one hand, I fully understand why people allow the IRS to send them a refund. For one, it's simple. It doesn't require the taxpayer to do anything other than collect a paycheck once a year from the IRS. Secondly, it's a way of forcing yourself to save money. If you have the penchant to spend as soon as the money comes in, getting a tax refund is a smarter way of "setting money aside."

However, setting money aside this way has a dangerous consequence: The IRS pays no interest on your refund. In other words, you're giving the IRS a free loan if you overpay on your taxes.

Consider for a moment that the stock market has risen by 8% to 10%, on average, throughout history. Now consider that through March 28 of this year, the average refund for tax year 2013 was $2,831. If taxpayers are missing this money throughout the year because they're overpaying on their taxes, then they could be forgoing an average annual gain of 8% to 10% on that money. While that may not sound like a lot, over a 40-year period, an individual could be cheating themselves out of more than $10,000 at the midpoint of the stock market's historic average return. Not to mention that inflation will likely devalue your free loan as it sits in the IRS' hands.

Figuring out how much you owe the IRS is the first and most important step in making sure you keep as much of your hard-earned cash as possible.