So you debited an expense account and credited an liability account before year end (Dec 31 for example).  Now do the exact same thing but reverse it.  Credit the expense account and debit the liability account and date it in the current year (Jan 01 for example).  

Ok, I wasn't sure which date to put! I am a student in bookkeeping right now so I shouldn't have estimated the bills right?

If I have a bill with a billing date in Dec of 2013 but the Due date is Feb 2014 and I just only received the bill in Feb what date do I put down the Dec date because it was for use in that month or Feb because it was paid in that month?

I appreciate the help!

Thank you!

Yes, it is okay to estimate bills.

The matching principle says you want to expense it in December since that was the month the product or service was used.  It doesn't matter when the invoice is received or paid.  The idea is to match revenue with expenses.  

One more thing: You said the bill date is December but you just received the invoice in February.  In the real world, I produce monthly financial statements and once those statements are done they are not changed.  If I receive an invoice in Feb for Dec, I must expense it in Feb.  This upsets the matching principle.  That's why bills are accrued.  If I know I get a phone bill every month for $50 but I haven't received an invoice, then I will expense $50 for that month anyway.