Thank you for your question.
If you are on cash accounting, you have to take your expenses in the year paid for.
You have to count your revenues in the year received.
Now the issue iwth cleared checks and the like is: you are considered to have constructive receipt in the year the check is given you to you. so you could receive a check on december 31, and it has to be included in 2008 income, even if it is not cashed at the bank until 2009.
You can only count expenses into the next calandar year under two circumstances:
1. You are on accrual accounting.
2. If you have net operating losses, you can take those looking back and then forward.
Under the accrual method, transactions are counted when the order is made, the item is delivered, or the services occur, regardless of when the money for them (receivables) is actually received or paid. In other words, income is counted when the sale occurs, and expenses are counted when you receive the goods or services. You don't have to wait until you see the money, or actually pay money out of your checking account, to record a transaction.
Under cash accounting you take expenses when they are paid, and you count cash when it is constructively received.
If you are already on cash accounting, which mos tsmall businesses are, then you can only change with the approval of the IRS.