Navis N4 Acheck: What It Is and How to Avoid Gate-In Failures
Acheck is the automated gate-in validation in Navis N4 that every container must pass before entering a Transnet Port Terminal. This guide explains what acheck checks, the most common reasons containers fail, and how to prevent acheck rejections at CTCT, DCT, CTMPT, and all TPT terminals.
What Is Acheck?
Acheck (also written as a-check, A-Check, or ACheck) is the automated validation process in Navis N4that runs when a truck arrives at a terminal gate. It's the system's way of verifying that a container has a valid pre-advise record and that all mandatory data is correct before allowing the container into the yard.
Think of acheck as the final automated gatekeeper. Every container at every Transnet Port Terminal — whether CTCT, DCT, CTMPT, Ngqura, or Port Elizabeth — must pass acheck to gate in.
What Does Acheck Validate?
The Navis N4 acheck process verifies:
- Pre-advise exists — A pre-advise record must be active in Navis N4
- Container number — Must be valid ISO 6346 format with correct check digit
- Booking reference — Must match the terminal's booking records
- Carrier mode — Must be set to Truck for road transport
- Vessel and voyage — Must match a scheduled vessel in N4
- Gate-in date — Must fall within the booking window
- No holds or restrictions — Container must be clear of customs or terminal holds
- Stack availability — Destination stack must be open
Top 5 Reasons for Acheck Failure
1. Carrier Mode Not Set to Truck
This is the single most common cause of acheck failure. When pre-advising manually under time pressure, operators frequently forget to set carrier mode or accidentally leave it on the wrong setting. Booking Buddy always sets carrier mode to Truck automatically.
2. Incorrect Container Number
A single transposed digit in a container number causes an immediate acheck failure. ISO 6346 container numbers have a built-in check digit — Booking Buddy validates this before submission.
3. Booking Reference Mismatch
The booking reference in the pre-advise must exactly match the terminal's records. Typos, extra spaces, or wrong booking numbers cause acheck to reject the container.
4. Gate-In Date Outside Window
Each booking has a valid date window. If the gate-in date in the pre-advise falls outside this window, acheck will reject the container. This is common when bookings are rescheduled but pre-advise dates aren't updated.
5. Stack Closed or Full
Even with a perfect pre-advise, acheck can fail if the destination stack at the terminal is closed or at capacity. Monitoring stack updates at CTCT, DCT, and CTMPT helps avoid this.
How to Prevent Acheck Failures
The best way to prevent acheck failures is to validate every field before submitting the pre-advise to Navis N4. Booking Buddy's built-in Validation Engine does exactly this — checking container numbers, carrier mode, booking references, vessel data, and gate-in dates against the same rules that acheck uses. By catching errors before they reach N4, Booking Buddy minimises gate-in rejections at every Transnet terminal.
For more information about the Navis N4 acheckvalidation process and Booking Buddy's approach to preventing failures, visit our dedicated acheck page.