Accrue expenses for non-PO invoices?

Summary:

Period-end accruals are automated when you use purchase orders, but when you don't use purchase orders, how do you accrue those expenses before receiving the invoice in the next period?

Content (required):

My client is new to using purchase orders, so most of their AP invoices will continue to be non-PO invoices. They tend to receive most of their supplier invoices at the start of the month (e.g. December), even though the expense was incurred in the previous month (e.g. November). They want a way to mass update the GL date on all of the supplier invoices received at the start of December before closing November, so that the invoices are accounted in the correct period. However, I am not aware of this functionality, and I think it's better practice to generate