Help needed with Unearned Income Account

We have to create a debit note to Unearned Income this month and credit A/R to be able to get something into production. The customer is sending in payment this month but it will not ship until January 2019. When it ships, an invoice will be generated. PLEASE help with this process giving the best way to process the invoice. Is it possible to have it hit Unearned Income during the invoicing process?