Invoice dates - Accrual vs actual

My company uses the accrual method of accounting. Up until working here, I had always worked with the cash basis. My question is when entering invoices, do I use the date on the invoice, or the last date that the invoice covers. We do have bills that we pay "in advance" like cell phone, but then others like electric and internet that are billed after the usage. I have always entered the bill as of the invoice date, but made note of the period covered. Which way is the correct way?