ACH validation in run time

I have validated the credit card in Authorize.net using the authOnlyTransaction method. I have also the option of ACH validation but there are some problems in validating that may be because of lack of knowledge in payment domain.

1. I tried to use the authorize.net but i have to specify the amount first.
2. It does not validate all the credentials but only routing number and bank name
3. I have to wait 2-3 days for the verification from the bank regarding the payment.

Question is, is there any method which i can use to validate the ACH on my webpage when user hit the verify button ? I have also tried to use the plaid but in the documentation it states that this also required some days to valid. Any kind of help would be much appreciated.

There is no way to get real time verification of a bank account through Authorize.Net. ACH works differently than credit cards and this is one of the limitations of it (the upside being lower cost associated with accepting ACH payments).

Plaid does offer account verification through an API which returns an immediate result. Plaid is not free, however.

If you provide a service or product and accept ACH payments, and don't want the risk associated waiting from verification that the account is valid or pay fees, then you should postpone allowing access to that service or shipping your good until payment clears. Otherwise, a service like Plaid is what you are looking for.