Before I get started let me state clearly and strongly that I AM NOT A TAX EXPERT but I do have a lot of experience in business and these are some of the things I have learned you can do to lower your taxes for this year.
There are two methods of accounting –Cash and Accrual. When you keep your books and file you taxes on a cash basis you can take expenses and deductions when you incur them, but when you use the accrual method you have to spread them out over the year and expense them when they occur in real time. Therefore for small online businesses I think you will find the cash method better and more advantageous. (Talk to your CPA before doing this so you can learn the rules).
Basically what you want to do this time of year is prepay any expenses you can and order merchandise for resale before the end of the year. This way you can take those expenses on your 2015 taxes. For example, just last week I prepaid my website hosting for the next three years). My CPA says I can take that entire expense this year.
Of course you only want to do this if you had a profitable year. If you are already in a loss situation this would only make it worse. And remember losses are not that bad if you are spending money that will make you a profit later. And also remember you can take losses against your regular income from a job if you have one.
If you have not yet started your business then December is a great month to do so because you will have expenses but little or no income so you can take those paper losses against any other income you have but you will already be set up to make money starting in January.