We'll be working in QuickBooks Online, so make sure you have access to that!
Returning the remaining balance has two steps; actually moving the funds via check or transfer, and accounting for it. We cover the accounting, and let you handle the banking.
To account for the release of funds back to the Client you'll need to create a Check in QuickBooks Online. Set the Client as the "Payee", and your IOLTA as the "Bank Account.
Next set the "Category" to the Client/Matter's liability account (usually called "Funds Held in Trust"). This tells the system which Client/Matter you're specifically pulling trust from.
Fill out the description and amount, then you're set! All that's left to do is actually transfer the funds.