It depends.  If your business is using the accrual method of accounting, then, yes, you enter your income and expenses as they are incurred (the date of the bill/invoice).  This would require the business to accrue the liability of the expense in 2017, even though the payment may not be made until 2018.  

If your business uses the cash method of accounting, then you can only deduct the expense when paid.

The accounting method for a business is typically set the first year of business and can only be changed in future years with IRS approval by completing Form 3115, Application for Change in Accounting Method.