Hello there, @molly14.

Yes, we can manually enter a handwritten check in QuickBooks Online. I'll guide you how:

     1. Go to the Accounting tab, then select Chart of Accounts.

     2. From the Chart of Accounts window, choose a Checking Account, then click View register.

     3. Select the Add check drop-down arrow, then choose Check.

     4. Enter the Date, select the Payee, and Account drop-down arrow.

     5. Put the Memo and Payment.

     6. Hit Save.

Also, you can handwritten the check, and then write check in QuickBooks Online.

Don't hesitate to touch base with me here in the Community if you need more help with this. I've always got your back and am always happy to help.