How do I properly close out an interest expense subaccount for a construction job we just completed in desktop?

Allow me to share a few information about closing out an interest expense account, Jeanettecaler.

In QuickBooks Desktop, you really don't have to close an interest expense subaccount manually. When you do reconciliation, you review your accounts to make sure they match your real-life bank and credit card statement. After this, you're now ready to close your books, which you may consider somewhat related to closing your account. 

As long as you reconcile your account on a monthly basis, QuickBooks adjusts your income and expense account so you'll be able to start a new fiscal year with a zero net income. You may want to set the interest expense subaccount inactive, follow the steps below:

1. Go to the Lists menu, then select Chart of Accounts.
2. Right-click on the account you want to make inactive, then select Edit Account.
3. Select the Account is inactive checkbox.
4. Select Save & Close.

Please check out this article for more information: Add, Edit, or Delete Accounts In QuickBooks Desktop. Furthermore, QuickBooks creates automatic adjustments in preparation for the coming year. I've added this article that will show you how to close your books: Close Your Books In QuickBooks Desktop. 

Reach out to us if you have any other questions about the interest expense subaccount. Remember, we're here to further assist you. 

@Jeanettecaler 

Do you want to close it out to the parent account so this particular subaccount can be made inactive?

If so, you can do a journal entry by debiting the parent account and crediting the subaccount for the balance.