Google announced on the AdSense blog that they have now added deductions and their reasons to the AdSense payment reports. So instead of just showing estimated versus finalized earnings, Google will show you why your finalized earnings are less than your estimated.

Google said:

Here is a picture of a sample payment report showing these deductions:

Last month, I saw a $20.13 deduction for “invalid traffic,” who knew. 🙂

Forum discussion at Google+.