Last Thursday, April 15, was Tax Day. Across the country, millions of taxpayers filed their state, federal and local income tax returns. On the same day, Americans in all 50 states held Tax Day tea parties to protest taxes, growing government spending and the ballooning government debt.

While the tea party movement is controversial to some, the passage of Tax Day is an appropriate time for Americans to think about how their government spends their money. For too many people there is a disconnect between government spending and taxes. Every program, every benefit and every tax break has to be paid for, by someone.

Too many people don't realize that government spending has to be paid for. That misconception could be related to a finding reported last week that 47 percent of Americans pay no federal income tax.

While that figure is stunning, it's important to remember that nearly everyone pays federal taxes through payroll deductions for Social Security and Medicare. Most people also pay plenty of other taxes, including sales taxes, excise taxes and property taxes.

Still, it's troubling that nearly half of all Americans pay no income tax, which remains the largest source of revenue for the federal government.

Those with no tax bill might think they have no "skin in the game" when it comes to federal spending or the rapidly growing federal deficit. For those not paying federal income taxes, unsustainable government spending could be seen as someone else's problem. But it's not. All Americans should be concerned about government spending and record-high federal budget deficits.

For that reason, there should be a minimum amount, say $100 to $500, that everyone pays in federal income tax. Even if there must be a Social Security offset, everyone should pay some amount in federal income taxes so that they feel they are part of the system — and care about government spending.

It's too easy to think of government spending as involving other people's money. If everyone pays some income tax, they'll realize it's their money being spent.

The passing of Tax Day also is a time to remind people of the estimated $400 billion annual "tax gap." That's the difference between what the Internal Revenue Service estimates is owed to the U.S. Treasury in federal income taxes and what is actually collected. Some of the tax gap can be explained by the complex tax code and people making honest mistakes. But most of the gap is the result of illegal tax avoidance, from not reporting income to stashing money in offshore tax havens.

If all the money owed to the U.S. Treasury was being collected, the extra $400 billion a year would go a long way toward bringing the budget into balance — at least until the massive bailouts and stimulus spending of recent months are included.

Tax cheats and those who under-report their income cause honest taxpayers to pay more. As a result, taxpayers should insist that the tax gap be eliminated — or cut dramatically — before any broad tax increases are considered by Congress.

Another problem with tax cheating and underreporting income is that it can be contagious. When honest taxpayers hear of more and more people falsely reporting income, or inflating their deductible expenses to decrease their tax bill, they can be tempted to cheat too.

Continued government failure to ensure higher income tax compliance will eventually threaten the entire system.

One category of tax cheats are many of the people who operate primarily in a cash world or are part of the underground economy, including both legal and illegal activities. For these people who do have income, but no W-2 form from an employer, the IRS is at a disadvantage. Finding ways to bring more of these people into the system so that they pay their fair share is another important job.

This segment of the economy is one of the arguments supporting a national sales tax. For those who are paid cash under the table or who might not honestly report all their income on their 1040 form, a federal sales tax would at least capture some of their federal obligation. To be fair — and revenue neutral — a national sales tax should be accompanied by a corresponding reduction in federal income taxes,.

Tax Day was for some a time for griping and complaining. On that, it's worth noting that griping about taxes should be directed at Congress, not the IRS, which is only collecting taxes approved by Congress.

Last week's Tax Day also was a time to think about the overly complicated tax code, which is thousands of pages long and full of loopholes generally put there by lawmakers backed by powerful special interests.

Concerns over government spending and the unfairness of the income tax system should not be limited to Tax Day protests. Taxpayers and voters should hammer away at these issues until elected officials in Washington, D.C., respond. And if they don't respond, it's time to send new officials to Washington.