According to customs and border patrol:
Details on ACH Debit
With ACH Debit, the payer transmits payment authorization to CBP, and CBP sends the payment information through the network to the payer's financial institution.
Benefits of ACH Debit
Obtain up to an additional 10 days to pay duties, taxes, and fees on quota and other special merchandise classes.
Reduce administrative processing and costs.
Pay all ABI statements in a central location.
Reduce administrative errors related to check processing.
Eliminate lost or stolen check problems.
Control cash flow by identifying the exact day to allocate funds.
ACH Debit Process
Step 1: The Filer Receives the Preliminary Statement. CBP generates a preliminary statement of entry summaries scheduled for payment and transmits it to the filer through ABI. The filer prints and reviews the statement. If the filer deletes an entry summary from the statement through ABI, a new statement amount is transmitted to the filer.
Step 2: The Filer Transmits ACH Payment Authorization. The filer transmits the payment authorization to CBP through ABI. The filer sends one ACH payment authorization per statement, usually the same day the statement and entry summaries are submitted to CBP. All ACH payment authorizations are initiated by the filer--CBP takes no payment steps until the ACH payment authorization is received and accepted.
Step 3: The Filer Receives A Confirmation Message. If the ACH payment authorization transmission is error free, the filer receives a message that the authorization has been accepted. If transmission errors occur, the filer receives an error message for each incorrect transmission until the problem is corrected and authorization is properly transmitted.
Step 4: The Filer Receives the Final Statement. CBP transmits a final statement to the filer, usually on the first business day after the payment authorization is received, accepted, and processed by CBP. The final statement lists all paid summaries and serves as a payment receipt.
Step 5: All Accounts are Credited and Debited. After ACH payment authorization is approved, funds transfer begins. CBP transmits payment information to the ACH processor bank and the Treasury account is credited. The ACH processor bank then transmits the data to the payer's bank. The payer's account is debited usually two business days after CBP accepts the initial payment authorization.