I prepared my tax return on two different tax sites and got two different numbers. I triple checked all of my documents and still came up different, why would this be?

[xmasbaby0]

We cannot see those sites and we cannot see what you entered or where in the software you entered the information.  You may think you entered everything the same---but the only way to spot what is different would be to print out both returns, lay them side by side and compare them line by line to see what is different.   All of the tax software programs must be checked and meet the IRS's approval.  Entering the same information into any of the tax programs should get the same results---one of the biggest variables is the user who enters the information.

[fanfare]

"All of the tax software programs must be checked and meet the IRS's approval. "

Believe it or not, tax prep software sometimes contains bugs.