America's corporate tax laws have been a point of contention between politicians for years.

Notoriously one of the most complicated systems in the world, some argue that the American tax system penalizes firms for bringing profits back to the United States and discourages saving for the future.

With the 2016 election on the horizon, corporate tax is an issue that is sure to spark a heated debate. Many have been criticizing those firms that have moved money offshore in order to avoid sky-high taxes, but others claim America's tax laws are forcing companies to find loopholes in order to preserve their profitability.

To add substance to the debate, published a report examining the tax rates for S&P 100 companies in order to get a better picture of how corporate taxes affect the country's biggest businesses.

The report found that the average S&P 100 company's tax rate was 11 percent higher than that of the top 3 percent of consumers.

Related Link: 6 Tax Stories This Think Tank Is Watching

The average overall tax rate for U.S. firms is 28.4 percent, though there is a high degree of deviation as rates varied from -2.5 percent to 2994.4 percent.

WalletHub also noted that tech companies are still depending on lower foreign tax rates with firms like Apple Inc. (NASDAQ: AAPL) and Cisco Systems, Inc. (NASDAQ: CSCO) are enjoying tax rates abroad that are more than 25 percent lower.

Financial services giant Morgan Stanley was the only firm found to have a tax benefit, as the company's overall rate was negative.

The firm was taxed at a rate of -2.5 percent in 2014 with federal taxes making up much of the credit at -44.9 percent.

Amgen is a biotech firm that markets, develops and manufactures pharmaceutical products in the United States and Europe.

The company's overall tax rate was the second lowest at just 7.6 percent. The firm's international tax rate was just 3.5 percent, and it paid 15.4 percent to the federal government.

General Electric also paid relatively low taxes in 2014; the firm's overall tax rate was 10.3 percent.

The infrastructure and financial services firm had negative state and federal tax rates: -4.3 percent and -2.3 percent, respectively.

General Motors paid a similar rate to General Electric with an overall tax rate of 10.6 percent.

While the firm's international tax rate was extremely high at 157.4 percent, General Motors had a negative federal tax rate of 35.9 percent.

Mondelez is a snack food and beverage company that sells to around 165 different countries across the globe.

Last year, the firm had negative income and paid 13.8 percent taxes overall. Much of those costs came from international taxes, which came in at 15.6 percent.

Energy exploration and production company Anadarko topped the list with the highest overall tax rate, as the company paid an overall rate of 2994.4 percent despite having a negative income in 2014.

The firm's international tax rate was 49.4 percent.

Oklahoma-based oil and gas firm Occidental Petroleum came in at number two on the list of highest taxes, with an overall rate of 109.3 percent.

The firm paid international taxes at a rate of 81.0 and avoided federal and state taxes with a negative income.

Devon Energy rounded out the top three highest corporate taxpayers, with an overall rate of 58.3 percent.

The firm paid a 40.2 percent tax rate to the federal government and a 2.5 percent rate to Oklahoma's state government.

Related Link: Report: Starbucks, Fiat Chrysler Found To Be Illegally Avoiding Taxes; Amazon, Apple Could Be Next

Financial services firm Citigroup had the highest tax rate of all S&P 100 companies excluding oil businesses.

The New York-based firm had an overall tax rate of 47.8 percent and paid 55.5 percent in federal taxes.

Health and wellbeing holding company Walgreens Boots Alliance paid an overall tax rate of 42.9 percent.

The firm's international tax rate was 17.5 percent, while its federal tax rate came to 41.1 percent.

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