Thanks for posting your concern in the Community space. I have some information with regards to your question about paying contractors from the mobile app using ACH.
At this time, you can pay vendors directly using ACH bank transfer right in QuickBooks Online Bill Pay. This allows the user to pay Bills electronically within QuickBooks Online.
While the feature isn't available in QuickBooks Online mobile apps, I encourage you to send feedback straight to our product developer to let them know you'd like this feature added in QuickBooks. QuickBooks Online is a constantly evolving platform and the voice of users, like yourself, helps steer the changes that occur.
Go to the Gear icon.
Enter your request/product suggestion, then click Next.
Select Feedback as the Category.
Click Send message.
Additionally, I want you to know that your voice matters and I'll be sending a product suggestion about your concern based on this interaction. Feedback is sent to the Development Team for determining what features and systems to implement for users.
This should provide information about paying vendors using ACH on the mobile app. If you have other questions aside from this, just drop a reply below. I'll be happy to answer. Have a nice day!