Microsoft is buying LinkedIn and they have so much cash on hand that they could pay for the professional social network four times over without ever needing to even pick up the phone to start dialing the number of a single bank. Yet, they want a loan for the purchase anyway. Why would a company that s as flush as Microsoft want to take on debt like that when it doesn t have to?The answer s simple   the loan equals a tax deduction for them, and the interest on the loan will lower their tax bill for years to come. Robert McIntyre, of Citizens For Tax Justice, says: It s an odd world where a company is awash in cash and chooses to make the acquisition with debts because they don t want to pay tax. That, combined with all the other ways they can game our tax system, will bring their total annual liability to rates that are far lower than the one corporate America, and Republicans, scream is too high.This particular loophole will allow Microsoft to avoid the 35 percent tax rate they d pay for repatriating cash they re holding overseas that s needed to buy LinkedIn without a loan. Exactly how much tax will they avoid paying just this year?$9 billion. And it s perfectly legal. In fact, most types of corporate tax evasion are perfectly legal.And that s just for one year. They ll avoid millions more on just this particular purchase in the years to come, in addition to all the other ways they ll avoid paying their fair share of taxes. They aren t the only ones doing this. Back in May, a study revealed that multinational corporations are avoiding paying at least $100 billion per year in taxes. That makes the tax evasion problem much worse than previously thought.Much has been made of things like corporate inversions, where corporations buy a smaller, overseas company for the purpose of shifting their headquarters out of the U.S. and thus, avoid our taxes. We also make a big deal about tax havens, such as the Cayman Islands and Switzerland, although we re starting to make headway with banks in countries that serve as tax shelters to put a stop to this type of evasion.But using loans when they re flush with cash is yet another tax evasion method. One might say that people with student loans and home mortgages are doing the same thing. However, people with those two particular types of debt are a) individuals, and b) aren t awash in the kind of cash a company like Microsoft is. So there s a huge difference there.Our official corporate tax rate might be 39.1 percent, and Republicans and our poor, downtrodden multinationals can whine about how high it is all they want. Their crying doesn t change the fact that, each year from 2006 to 2012, more than 60 percent of our corporations paid zero in federal income taxes. You can bet all the benefits they get from loans, like Microsoft is doing, contribute heavily to that. There is nothing that justifies their whining.Think this is just good business? Sure. From a purely profit-oriented perspective, anything that lowers costs is good because it raises the bottom line. There are real-world consequences though, and one of them is a country, like ours, that shifts its tax burden onto individuals who work, and work, and work for these very corporations, and can t bring in enough revenue to actually function properly.Microsoft will buy LinkedIn however it wants. But this, right here, is a perfect example of why our tax code needs to be overhauled. There s no reason at all Microsoft should be able to get a loan and deduct it from its taxes when it has four times the cash it needs to buy LinkedIn. There just isn t.Featured image by David Ramos/Getty Images