Which Tax Year to Claim Year End Deductible Business Expenses

I paid for some expenses, which are tax deductible, at the end of the year. I paid for them online and set it up as an ACH electronic draft so the money would be paid out of my bank account. The expenses did not finalize until the new year began. Can I deduct it in the year that I paid it or do I have to wait until the next years taxes since the transaction date is in the following year? Furthermore, if the answer is inconsistent with my past practice for previous tax years do I need to go and amend prior tax returns? Thank you in advance for your answer.

Which Tax Year to Claim Year End Deductible Business Expenses