Reverse planning in Business Central lets you run a true MRP calculation where you break top-level demand down into lower-level components, but keep full control over each level before you commit to orders.
You do this by working one low-level code at a time instead of running a single full batch job. Calculate the top level, review the suggestions, adjust quantities, carry the lines into the reverse planning worksheet, and then move on to the next level.
Two settings make this work. Enable Include planning lines so the calculation reads the planning lines you have already created. Enable Skip if already planned so it leaves those lines untouched and does not re-plan items you have already handled.
If you instead check Run for all low-level codes in the template, the batch runs through every level at once and you cannot modify the orders per level. That option is fast, but it removes your chance to adjust quantities along the way.
How reverse planning breaks demand into low-level codes
When you want a true MRP that breaks the top-level suggestions down into further low-level codes, you can do it in reverse planning and still only create new orders. You can run it as a full batch job, but in practice you often run it one level at a time.
That means you can calculate a simple MRP that finds only the critical items, meaning the items that are critical right now. You start at the top, look at what the calculation suggests, and decide what to carry forward.
The two template fields that control the planning behaviour
The template has two fields that matter here.
- Include planning lines: include all the planning lines that already exist in the worksheet so the calculation takes them into account.
- Skip if already planned: leave items that have already been planned untouched, even if their demand has changed.
When you first run it, the reverse planning worksheet is empty. You calculate the simple MRP, and it suggests quantities to order based on your parameters. You set the action message on the lines, check the ones you want, and carry them out to transfer them into the reverse planning worksheet.
How dependent demand carries through the levels
Say the calculation creates five lines that generate dependent demand. If you open the first line and look at its components, these are standard Business Central planning components. They live in the planning component line table, which is a standard table, and they create dependent demand.
Here is where you need to be aware of what happens. If you look at the components for a sports bike, you also have demand for lamps and brakes. And if you look in the journal, you may already have created planning lines for lamps.
When you plan the next level and calculate the simple MRP again, you are doing the same thing as before. But because you checked Include planning lines, it includes the dependent demand, and because you checked Skip if already planned, it leaves the items you already planned in the journal alone. So it does not plan the lamp again, even if the required quantity increased.
You then suggest the quantity to order, get the new lines, set the action message, and carry them out. This lets you work in small iterations, adding to what is already in the worksheet.
Running for all low-level codes versus working level by level
If you want to do a real MRP across all levels, you have two options.
The first option is to calculate the way described above and filter on low-level code each time you run it. You start by filtering on low-level code zero, run it, then move to the next code, and so on.
The second option is to use a template where you check Run for all low-level codes. That setting runs through every low-level code in one go.
The limitation of the second option is that you cannot modify the orders per low-level code. If you plan the first level and then want to change the quantities, it is already too late, because the batch has run through everything.
This is why the combination of Include planning lines, Skip if already planned, and filtering on low-level code is the more controlled approach. You leave the lines in the reverse planning worksheet, calculate per low-level code, and fill up the worksheet as you go along.
Q&A
What does the Include planning lines setting do in reverse planning?
It tells the MRP calculation to read the planning lines that already exist in the worksheet, so the calculation takes the dependent demand from those lines into account when planning the next level.
What does Skip if already planned do?
It leaves items that you have already planned untouched, even if their demand increased. For example, if you already created a planning line for a lamp, the calculation will not plan the lamp again.
Why would you plan one low-level code at a time instead of running all levels at once?
Because running all low-level codes in one batch does not let you modify the orders per level. If you plan the first level and want to adjust quantities, it is too late once the batch has gone through everything. Working one level at a time keeps you in control of the quantities before you move on.
Can you still only create new orders when using reverse planning for a true MRP?
Yes. You can break the top-level suggestions down into lower-level codes in reverse planning and still only create new orders.
What table holds the dependent demand created by reverse planning?
The dependent demand is created as standard Business Central planning components, stored in the planning component line table, which is a standard table.