Bonus Depreciation and Small Business Expense Extension Act - Amends the Internal Revenue Code to extend for one year: (1) bonus depreciation; (2) the 100% expensing allowance for depreciable business assets; (3) the election to accelerate the alternative minimum tax (AMT) credit in lieu of bonus depreciation; and (4) the increased expensing allowance for tangible real and personal property, including computer software and leasehold, restaurant, and retail improvement property.