If there is a change in method from one period to another, the financial statements must clearly indicate that change. Readers of statements an assume that this takes place all the time unless notified otherwise. This prevents people from manipulating figures by changing accounting methods.
If you're excluding something form the financial statement, it shouldn't affect the net income/loss of the company. Eg. there was a $10 invoice error, but the company earned $500,000 net income. Not a big deal because $10 isn't a big deal.