Let me step in and assist you with your concern today.
Currently, the option to add a signature and print it on a check is only available in QuickBooks Desktop. For now, you can affix the signature manually on every check you’ve printed or integrate a supported E-signature third-party application.
To check for apps compatible with QBO:
Go to Apps.
Click Finds Apps.
Type "digital checks/signature" in the Search for an app field (see screenshot below).
If you have found the app you're looking for, just click Get App Now.
Having this feature in QBO is indeed a great idea and I’d appreciate it if you send your product suggestions straight to our Developers for consideration in future updates.
Here’s how to send a product request: 1. Click the Gear icon. 2. Select Feedback. 3. Enter your suggestion. 4. Click Next. 5. Click Skip and send message. 6. Select a Category. 7. Click Send message.