Flushing Methods in Business Central (Version 27)

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After 15 years on Business Central and NAV (and 30 in ERP overall) in factories across Greece and the UK, I can tell you one thing for sure: choosing the right flushing method can make daily life on the shop floor smooth or turn it into a constant headache. I’ve seen both sides many times.

Flushing methods are simply the rules that tell Business Central when and how to deduct (consume) raw materials from inventory during production. Get them right and your on-hand stock stays accurate, WIP is honest, and costing is clean. Get them wrong and you’ll spend half your time posting manual corrections and explaining strange variances to finance.

Here’s how I explain and use them in real factories.

The Four Main Flushing Methods

Manual

This is the one I recommend when you need full control. Nothing is consumed automatically. You or the operators have to post the Consumption Journal or Production Journal with the actual quantity used.

I use Manual for expensive parts, lot or serial tracked items, or when usage and scrap vary a lot. It gives you the most accurate lot traceability, but it does require discipline from the shop floor team.

Forward

Business Central automatically consumes the expected quantity as soon as the production order is Released (or when the linked operation starts if you use Routing Link Codes).

This works well for stable, repetitive production with cheap and predictable components. Cost moves to WIP early and you do less manual posting. The downside is that if you scrap material or usage changes, you have to post manual adjustments later.

Backward

This is my favourite for many factories. Consumption is posted automatically when you finish the order (or when each operation finishes if you use Routing Link Codes). It bases the consumption on the actual output quantity.

It is clean, simple, and keeps consumption aligned with what was really produced. I like it for short production cycles where you don’t need to track material movement step by step.

Pick + Forward and Pick + Backward

These are the versions for locations that use warehouse picks. They work exactly like Forward or Backward, but they first create a Warehouse Pick to move the stock to the To-Production bin before consumption is posted.

You need the To-Production Bin Code set on the location. I use these a lot in UK plants with advanced warehousing, so you still get the physical pick process but keep the automatic consumption.

Things That Make a Big Difference in Practice

Routing Link Codes are extremely useful. They let you flush components at specific operations instead of the whole order level, which gives you much better timing and WIP visibility.

Assembly Orders behave differently. They always post consumption together with output (basically backward-style) and don’t create WIP at all. And Jobs (the Project module) don’t use flushing methods at all. You post consumption manually through the Job Journal.

The Hidden Hierarchy: Where Does Business Central Look?

One technical detail that often causes confusion is the hierarchy of where BC actually reads the flushing method from. It doesn’t just blindly look at the Item Card. The system evaluates this in a very specific order:

1. Routing Line: If a specific flushing method is defined on the routing line for an operation, it takes absolute priority and overrides everything else.
2. Stockkeeping Unit (SKU) Card: If you use SKUs for multi-location manufacturing setups, BC looks at the SKU card for that specific location before it checks the main item card.
3. Item Card: This is the default base setting. It acts as the final fallback if nothing is specified on the SKU or Routing.

If you are experiencing unexpected consumption behavior on the shop floor, always check if an active SKU or a Routing Line setup is secretly overriding your main Item Card settings.

My Practical Advice from the Field

In smaller Greek workshops I usually go with Backward because it is simple and accurate.

In larger UK plants with proper warehouse processes I often choose Pick + Backward so the warehouse team still does the physical movement.

The biggest mistake I see is changing the flushing method on a production order after it has already been released. If Forward has already consumed the material, switching to Manual later does not undo it. You have to post an adjustment.

Another common error is using Forward without Routing Link Codes on a complex routing. Everything gets consumed at release, even if the first operation hasn’t started yet.

Quick Decision Guide I Give to Clients

For high-value or lot/serial tracked parts, go Manual. For stable, low-cost, repetitive items, Forward (or Pick + Forward if you have warehousing). When you want consumption to match actual output, use Backward or Pick + Backward. And if your site uses advanced warehousing with proper picks, default to one of the Pick variants.

Flushing methods are small settings on the Item Card, but they have a huge impact on daily operations, inventory accuracy, and costing. Choose them carefully, document your decision per item group, and review them once a year when you do your standard cost update.

If you are struggling with flushing behaviour on your production orders right now, feel free to describe the situation. I have seen almost every possible combination over the years and I’m happy to help.