NACHA Glossary

Overview

This glossary covers the key NACHA and ACH terms you'll encounter when using FISTWorks. Terms are grouped by concept to make it easier to understand how the pieces fit together.

Routing Numbers

What Is a Routing Number?

A routing number (also called an ABA routing number or RTN) is a 9-digit number that identifies a specific financial institution. It's printed on the bottom-left of paper checks and is required for all ACH transactions.

Format: 9 digits, where the last digit is a check digit calculated from the first 8.

Example: 021000021 (JPMorgan Chase)

Check Digit

The 9th digit of a routing number is a check digit calculated using a specific algorithm (the ABA checksum). FISTWorks automatically validates check digits when you enter routing numbers, catching typos before they cause file rejections.

ODFI — Originating Depository Financial Institution

The ODFI is your company's bank — the bank where you submit your ACH files. The first 8 digits of the ODFI's routing number appear in every batch header and are used to generate trace numbers.

In FISTWorks, this is the Originating DFI field in your originator setup.

RDFI — Receiving Depository Financial Institution

The RDFI is the recipient's bank — the bank that receives and processes the ACH entries. Each entry detail record includes the RDFI's routing number so the ACH network knows where to deliver the transaction.

In FISTWorks, this is the Routing Number you enter for each recipient.

Account Types

Checking vs. Savings

ACH transactions use different transaction codes depending on whether the target account is checking or savings:

When you select "Checking" or "Savings" for a recipient in FISTWorks, the system automatically uses the correct transaction code.

DFI Account Number

The DFI Account Number is the recipient's bank account number. In the NACHA file format, this is a 17-character field that is left-justified and padded with spaces. Account numbers can contain letters (some credit unions use alphanumeric account numbers).

Transaction Codes

Transaction codes are 2-digit numbers in each entry detail record that tell the receiving bank exactly what to do with the transaction.

Credit Codes (Sending Money)

Debit Codes (Collecting Money)

Prenotes

A prenote (pre-notification) is a zero-dollar test transaction sent before the first real payment. It verifies that the routing number and account number are valid and that the account can receive the intended transaction type. Prenotes use codes 23/28 (checking) or 33/38 (savings).

Company Identification

The Company Identification is a 10-character field in the batch header that identifies the company originating the ACH entries. It is typically formatted as:

• 1 + 9-digit EIN (Employer Identification Number / Tax ID)
• Example: 1123456789 (where 123456789 is the EIN)

Your bank may assign a different format. This value is configured in FISTWorks under originator setup as Company ID.

Immediate Origin and Destination

Immediate Origin

The Immediate Origin identifies the entity sending the ACH file. It appears in the file header record (position 14-23). Typically formatted as 1 followed by a 9-digit Tax ID, but your bank may provide a specific value.

Immediate Destination

The Immediate Destination identifies the bank receiving the ACH file for processing. It appears in the file header record (position 4-13). This is usually the 9-digit routing number of your ODFI, padded to 10 characters with a leading space.

In FISTWorks, this is the Destination Bank you select when creating a draft.

Batch and File Structure

ACH File Structure

A NACHA ACH file has a fixed hierarchy:

File Header (Record Type 1) — one per file
  Batch Header (Record Type 5) — one per batch
    Entry Detail (Record Type 6) — one per transaction
      Addenda (Record Type 7) — optional, attached to entries
  Batch Control (Record Type 8) — one per batch
File Control (Record Type 9) — one per file

Every record is exactly 94 characters wide.

Batch Number

Each batch within a file gets an ascending batch number (7 digits, starting at 0000001). The batch number appears in both the batch header and batch control records and must match. FISTWorks assigns batch numbers automatically.

Trace Number

Every entry detail record has a unique trace number (15 digits). It is formed by combining:

• The ODFI routing number (first 8 digits)
• A 7-digit sequence number (ascending within the batch)

Example: 02100002100000001 = ODFI routing 02100021 + sequence 0000001

Trace numbers uniquely identify each transaction and are used for tracking and return matching. FISTWorks generates trace numbers automatically.

Service Class Code

The service class code in the batch header indicates what types of transactions the batch contains:

FISTWorks calculates the service class code automatically based on the entries you add to each batch.

Transaction Amounts

Amount Format

In the NACHA file format, amounts are stored as 10-digit integers in cents (no decimal point). For example:

FISTWorks handles this conversion automatically — you enter dollar amounts with decimals, and the system formats them correctly in the ACH file.

Maximum Amount

The maximum amount per entry is $99,999,999.99 (the largest number that fits in 10 digits as cents).

Effective Entry Date

The effective entry date is when you want the transactions to settle (funds actually move). Key rules:

• Must be a valid banking day (weekday, not a Federal Reserve holiday)
• Typically 1-2 business days from the file submission date
• Banks may process files received before their cutoff time for next-day settlement
• Same-day ACH is available for files submitted before specific cutoff times (typically 2:45 PM ET)

FISTWorks defaults the effective date to the next business day.

Company Descriptive Date

The Company Descriptive Date is an optional 6-character date field (YYMMDD) in the batch header record (positions 64-69). Unlike the effective entry date, this field is informational only — it does not affect when transactions settle.

Its purpose is to communicate a meaningful date to the receiver for reconciliation. Common uses include:

• Payroll period end date — so employees know which pay period the deposit covers
• Invoice date — so vendors can match the payment to a specific invoice
• Billing cycle date — so customers know which billing period a debit covers

Example: A payroll batch with an effective date of February 28 might use a Company Descriptive Date of 260215 (February 15) to indicate the pay period ending date.

In FISTWorks, this field is optional when creating a batch. If left blank, it defaults to today's date at file generation time.

Addenda Records

An addenda record (Record Type 7) attaches additional information to an entry detail record. The most common use is carrying payment-related information such as:

• Invoice numbers
• Purchase order references
• Remittance details
• Reason codes for returns

Addenda records are required for CTX entries and optional for CCD entries. Each addenda record can hold up to 80 characters of payment-related information.

The Addenda Record Indicator field in the entry detail record is set to 1 when addenda records are present, or 0 when they are not.

File ID Modifier

The File ID Modifier (position 34 in the file header) is a single character (A-Z, then 0-9) that uniquely identifies files created on the same date by the same originator. If you generate only one file per day, it will always be A. If you generate multiple files in one day, they should increment: A, B, C, and so on.

SEC Codes

For a detailed guide to all 12 Standard Entry Class codes, see the SEC Codes Reference.