ACH refers to chargebacks as returns. It is not possible to defend ACH returns. You have the following options:
To reduce the risk of chargebacks, you can use an external account validation service.
In case of a Notification of Change, you can prevent future returns by asking the customer to update their account details.
In some cases you can retry the payment.
Causes of ACH chargebacks
Because the ACH network is unable to provide real-time authorizations, an authorised payment can be reversed due to insufficient funds. Such chargebacks usually happen three to five days after the date of the direct debit payment. Also, the customer can initiate a chargeback up to 60 days from the payment date, after the funds have been settled to your account. This can happen when:
The customer did not formally agree to the charge, or revoked their agreement.
The charge is processed earlier than the agreed date.
The charge is not the same as the agreed amount.
This is different from credit card transactions, where a customer can initiate a chargeback by claiming that a product or service was not what they expected.