American corporations pay about 40 percent of their revenue in taxes every year. Though it varies with state and local tax rates, it's clear that the biggest companies aren't making their billions because of large-scale tax avoidance. Some pay more than half their net income to various governments. Here's a list of the 10 companies, compiled by Forbes using data from FactSet Research Systems, that paid the most in taxes last year: 

1. Exxon Mobil (NYSE:XOM) paid $31 billion. 

Based in Texas, Exxon tops the list, with an effective tax rate of 39 percent (net income was $45 billion). 

2. Chevron Corporation (NYSE:CVX) paid $20 billion. 

Oil giant Chevron wound up paying one of the highest effective tax rates: 43 percent (net income was $26 billion). 

3.  Apple Computer (NASDAQ:AAPL) paid $14.2 billion. 

In California, Apple wound up paying 25 percent in taxes (net income was $41.7 billion). 

4. Wells Fargo & Co (NYSE:WFC) paid $9.2 billion. 

San Francisco-based Wells Fargo paid 31.2 percent in taxes (net income was $19.8 billion). 

5. JPMorgan Chase & Co  (NYSE:JPM) paid $8.1 billion. 

Back in New York, JPMorgan Chase handed over 26 percent of its revenue in taxes (net income was $22.9 billion). 

6. Wal-Mart Stores, Inc. (NYSE:WMT) paid $8 billion. 

The international retail giant, based in Arkansas, paid 31 percent in taxes (net income was $17 billion). 

7. ConocoPhillips (NYSE:COP) paid 7.9 billion. 

With the highest tax rate of the biggest corporate tax payers, most of ConocoPhillips' revenue went to pay taxes, which reached an effective rate of 51.5 percent (net income of $8.4 billion). 

8. Berkshire Hathaway (NYSE:BRK.A) paid $6.9 billion.

Warren Buffet’s investment vehicle paid a relatively low 28 percent (net income was $14.8 billion).

9. International Business Machines Corp. (NYSE:IBM) paid $5.3 billion.

New York-based software and IT giant IBM paid 24 percent (net income was $16.6 billion).

10. Microsoft Corporation (NASDAQ:MSFT) paid $4.6 billion.

Rounding out the top 10 list, Washington-based Microsoft paid 22.8 percent of its revenue in taxes (net income was $15.5 billion).