Thanks for reaching out to the Community, Jaime78.

The fees for customers paying invoices with an ACH convenience fee are based on a percentage. You can find the current percentage of fees for ACH payments on our QuickBooks Payments Pricing page.

When you're ready, you can create an invoice with the customer's convenience fee.

Here's how:
 

1. In your left navigation bar, go to Customers, then Create invoice.
2. Leave all payment methods turned off. You can go to Manage, then Payments on an invoice to change which payment methods are available to the recipient. Under your Your customer pays the fee header, you should see ACH bank payments turned On.
3. If there's a particular way you prefer to be paid, add a comment in the Payment instructions field, or in the body of your email.
4. When you're ready to send the invoice, go to Review and send, then select Send invoice.

I've also included a detailed resource about working with this feature which may come in handy moving forward: Let your customers pay invoices by ACH bank payment with a convenience fee

Don't hesitate to reach out if you have more questions. Have a wonderful Thursday!

$25 dollars flat which is illogical.  They turned that on by default end of last year and we just realized it.  So our customers that do not have ACH or Credit cards enabled within QBO still get an option to pay via ach with our company branding included.  Then when they click through it adds a 25 dollar convenience fee for any ACH payment amount and sticks it right below the payment amount directly below our logo.  We turned it off QBO too greedy on this one...

Agree, we were shocked that Intuit is charging the customer $25 to pay via ACH.

@JLKOCHAN 

If you are B2B, you can use a 3rd party processor to integrate with QB and accept ACH payments for free.