USA Just received invoices from contractor for work performed in 2016

[BillLumbergh]

A contractor of ours (who is now an employee, by the way) just submitted invoices from 2016 that they forgot to send to us last year.

SInce I just received these a few days ago, is it OK to enter these as 2017 expenses and issue a 1099-MISC for 2017, or would the fact that they are now a full-time employee complicate things further? Accrual basis Accounting.

Thanks.