How do I remove an unrecognized deposit from 2018? those books were closed and and it has sat in the banking as a deposit but cannot be matched to anything in 2019

Thanks for posting in the Community, @tricia15. 

As long your 2018 books are matched with your bank statement, you can exclude the unrecognized deposit in the Banking tab. This way, it won't appear on your register or financial reports. I'm here to guide you through the steps. 

1. Go to Banking from the left menu. 
2. Select the For Review tab.
3. Check the box of the unrecognized deposit. 
4. Choose Exclude Selected from the Batch actions drop-down. 

The screenshot below show you the steps. For detailed instructions, go through this article: Exclude Expenses From Downloaded Transactions. 

Once done, you can now close your 2019 books. As always, visit this website: Reconcile Workflow. This link covers all the information from starting, fixing differences, and completing the reconciliation process. Just go to the QuickBooks Online section on every scenario. 

I'm always here to help if you need anything else. Have a good day, @tricia15.