I have noticed an item in my Balance Sheet titled Unrestricted Net Assets. Can anyone explain to me what that is?

In QuickBooks Online, Unrestricted Net Assets is the not-for-profit equivalent of Retained Earnings.

When your organisation is set up as a not-for-profit entity, QuickBooks uses not-for-profit terminology in the equity section of the Balance Sheet. 

The balance in Unrestricted Net Assets represents accumulated net income from prior financial years. At the beginning of each new financial year, QuickBooks automatically transfers the previous year’s net income to this account.

To review the transactions behind the balance, click the amount on the Balance Sheet. This opens a report showing the historical net income that makes up the figure.

If you have any further questions, please feel free to ask.