Business Central calculates low-level codes in two ways. You can run a Batch Job manually, or you can let the system calculate automatically by enabling Dynamic Low-Level Code in the manufacturing setup.
The recommended approach is to enable Dynamic Low-Level Code. When you turn on this setting, Business Central calculates the low-level code automatically every time you certify a production BOM.
The dynamic calculation catches circular references in your BOM hierarchy. If you accidentally make an item part of itself through several levels, the system blocks certification and returns an error stating that the calculation exceeds 50 levels.
The two methods for calculating low-level codes in Business Central
The first method is a Batch Job that you run manually. From the main menu you search for Low-level Code (LLC), choose Calculate Low-Level Code, and confirm. The job then runs through the entire item hierarchy and calculates the codes.
This works fine on small data sets. But if you have 50,000 items spread across ten levels of hierarchy, the Batch Job becomes heavy to run.
The second method is the automatic calculation, controlled by a check mark called Dynamic Low-Level Code in the manufacturing setup. This is the normal and most used way of handling low-level codes. When the check mark is set, the system calculates the low-level code automatically whenever you certify a production BOM, so you never have to think about running the job yourself.
How Dynamic Low-Level Code catches circular references
The automatic calculation does more than save you a manual step. It also protects your data from circular references in the BOM structure.
Take an example with a Front Hub that is part of a bike. That gives you a hierarchy where the bike sits above the Front Hub. If you then add the bike as a line on the Front Hub’s production BOM, you are telling the system that the bike is part of the Front Hub, and the Front Hub is part of the bike at the same time. That is not possible.
When you try to certify the BOM, the dynamic LLC calculation detects the problem. The error message says it exceeds 50 levels, because the system keeps trying to calculate the same loop again and again with no end. Certification is blocked until you fix it.
To resolve it, you remove the bike from the line, make sure the hierarchy is correct, and then certify the BOM again.
Why deep hierarchies make circular references hard to find
Finding the source of the error can be complex when you have very deep hierarchies. A circular reference is not a simple top-level problem. The moment you add the bike to the line, you create a loop that runs through several levels, and it can take some work to pinpoint exactly where it goes wrong.
This is a very common mistake for manufacturing customers. The recommendation is clear: set the Dynamic Low-Level Code check mark in the manufacturing setup. You get automatic calculation and an early warning whenever a circular reference sneaks into your BOM structure.
Q&A
What are the two ways to calculate low-level codes in Business Central?
You can run a manual Batch Job by searching for Low-level Code from the main menu and choosing Calculate Low-Level Code. Or you can enable Dynamic Low-Level Code in the manufacturing setup, which makes the system calculate automatically when you certify a production BOM.
Which method for calculating low-level codes is recommended?
Enable Dynamic Low-Level Code in the manufacturing setup. It is the normal and most used approach, it removes the need to run a manual job, and it warns you about circular references when you certify a BOM.
Why is the Batch Job slow on large data sets?
The Batch Job calculates codes through the entire item hierarchy. With 50,000 items across ten levels of hierarchy, this becomes heavy and slow to run.
What does the error about exceeding 50 levels mean when certifying a BOM?
It means you have a circular reference in your BOM. An item is set up as part of itself through the hierarchy, so the system loops endlessly trying to calculate the low-level code. Remove the offending line, correct the hierarchy, and certify again.
What is a circular reference in a production BOM?
It happens when an item is part of itself through the hierarchy. For example, if a Front Hub is part of a bike and you also add the bike to the Front Hub’s BOM, the bike becomes part of the Front Hub and the Front Hub part of the bike at the same time, which is not possible.