I want to allow clients to pay via ACH. Is there a way to turn on this function for all clients and not have to do it invoice by invoice? Thanks!

Yes, you can set the ACH as your customer's default payment method, @lindmediaco06. I'm glad to outline the complete steps to achieve your tasks. 

You need to edit the invoice template and choose "Bank Transfer " as the accepted form of payment. This way, your customers' primary payment method is ACH.

 Here's How:

1. Go to the Gear icon at the top and select Customer Form styles.
2. Find the template, then click Edit under Action.
3. Go to the Payments tab and ensure only Bank transfer is checked.
4. Click Done. 

You can set that template as your default if you want to. This way, we can ensure that your customer can pay you via ACH. 

For more details, see this article: Customize invoices, estimates, and sales receipts in QuickBooks Online,

Check out these articles below to get answers to the commonly asked questions about ACH payments in QuickBooks:

• Accept ACH payments and eChecks
• What are the fees for QuickBooks Payments?

If you have more questions about QuickBooks, feel free to come back. The Community is always around to help in any way that we can.