ACH transfers can fail for a variety of reasons including but not limited to insufficient funds, inability to locate the account, incompatible accounts that cannot perform ACH transfers, or action by the bank or account owner to stop payment.
If an ACH transfer fails, you will get an email informing you of this. Since you haven't paid for the purchase, the trade will be reversed, and the associated Bitcoin will be returned to the market. You will notice those funds removed from your Swan dashboard and a reversal will be noted in your Deposits tab. To mitigate fraud and therefore keep our fees low, there are no exceptions to this policy.
If an ACH transfer fails and the Bitcoin purchase has not yet taken place, then that scheduled purchase will not take place.
We cannot hold negative balances and wait for you to fund an account that has gone negative. It is your responsibility to ensure that the bank account on file is accurate and well funded prior to submitting a purchase order. Please do not try to time purchases to funds settling into your bank account, as funds settlement at banks is not a real-time process and may be delayed by any number of reasons.