Thank you for posting here in the Community, @SetxFire .

Allow me to step in and help you turn on the signature function in QuickBooks Online (QBO) app.

Once you capture signatures for your invoices or estimates, they will automatically be embedded in that transaction.

iOS

1. From the Menu ☰, select Estimates or Invoices.
2. Select an existing transaction or create a new one.
3. Add any necessary information.
4. Select Save.
5. Select Get Signature.
6. Have your customer sign with their finger.
7. Select Done.

Android

1. From the Menu ☰, select Estimates or Invoices.
2. Select an existing transaction or create a new one.
3. Add any necessary information.
4. Select Done.
5. Select Get Signature.
6. Have your customer sign with their finger.
7. Select Done.

If you wish to design and personalize your invoices, you may read through this article: Customize sales forms.

Please get back here if you have additional questions about managing your sales transactions. Have a great day!