Interperiod income tax allocation procedures are appropriate when differences between net income for tax purposes and financial reporting occur because, even though financial accounting principles and tax laws concur on the item to be recognized as revenues and expenses, they don't concur on the timing of the recognition. differences between net income for tax purposes and financial reporting occur because tax laws and financial accounting principles do not concur on the items to be recognized as revenue and expense. an extraordinary loss will cause the amount of income tax expense to be less than the tax on ordinary net income. an extraordinary gain will cause the amount of income tax expense to be greater than the tax on ordinary net income