Inventory and costing in Dynamics 365 F&O

This is the station where people arriving from other systems come unstuck, because it contains an idea they have no equivalent for.

The question it answers sounds strange to anybody who has not worked on this product: how does a month’s profit change after the month has ended?

The physical and financial update

Every inventory transaction here has two stages rather than one.

Stage	Document	What it establishes
Physical	Product receipt, packing slip	The goods moved — at an estimated cost
Financial	Vendor invoice, customer invoice	The value settled — at actual cost

The item model group — designed in station three — decides whether the physical stage posts to the ledger or is recorded in quantity only.

That is the setting behind half of all user questions: “why did the inventory balance in the ledger move when I have not invoiced?” — because the physical update posts. “Why did it not move?” — because it does not. The answer is in the group rather than in the transaction.

Costing methods

Method	Where it fits	Its price
Weighted average	Trading and distribution	Hides why the cost changed
FIFO	Shelf life and batches	Heavy under high volume
Standard cost	Manufacturing and performance control	Needs monthly variance analysis
Moving average	Continuous movement with no periodic close	Closes the door on retrospective adjustment

The choice sits on the item model group — a class of items rather than the company. Raw materials at standard and purchased goods at average in the same company is entirely correct.

The rule projects get wrong: standard cost is not “the advanced option”. It is the one that assumes somebody analyses variances every month. Choose it without that person and you have a variance account swelling with no reader.

Inventory close — the core of this station

All month, issues post at an estimated cost. At the moment of sale the system does not know which receipt the issued quantity will ultimately be matched against — because a receipt at a different price may arrive tomorrow.

Then inventory close runs, matching every issue to its corresponding receipt under the chosen method, and posting the cost difference as an adjustment.

What that does in practice:

• Cost of goods sold changes after the run, so the month’s margin changes.
• The book value of inventory settles on a number that can be reconciled.
• Anybody who has not run it has no final figures, however complete the report looks.

The governing rule: inventory close runs before the ledger period closes, not after. Reverse the order and the adjustments land in the following period, so September’s cost becomes October’s — an error only discovered when somebody asks why October’s margin is low.

There is a lighter recalculation that updates costs without closing the period, used during the month rather than instead of the close.

This manufacturing depth is one of the reasons for the price gap against its smaller sibling, and it is set out in the Dynamics 365 Finance & Operations guide.

Three symptoms read back to their cause

After go-live, complaints arrive as symptoms. Your job is translating them.

What the user says	The likely cause
“The item cost on the report differs from the one on the sales order”	Inventory close has not run — the report is final, the order estimated
“The inventory balance in the ledger does not match the stock report”	Physical movements not posted to the ledger, or an incomplete close
“The month’s margin changed after we closed it”	Adjustments fell into the following period — the order was reversed

The second is the most confusing because it looks like a system fault. It is not: the difference between the two reports is exactly the value of what moved physically and has not yet been accounted for. Understand that and you read the difference instead of raising it.

The single diagnostic rule: before opening any ticket about inventory figures, ask when inventory close last ran. Half of them close on that question alone.

This station’s exercise

In a spreadsheet first, then in the system if the environment is open.

1. Buy the same item three times at three prices and sell some of it. Compute the cost at weighted average, then at FIFO. The gap is what you are choosing.
2. Reorder the events: a sale before the last receipt, then after it. Watch the order change the close’s result.
3. Compute the expected adjustment journal before running the close, then compare.
4. Write the right method and the reason, in one line, for every item category in a company you know.

What you actually do in this station

• Do the exercise by hand in a spreadsheet. Compute it once and you understand it in any system.
• Post a packing slip and an invoice on one transaction, and distinguish the two journals.
• Run inventory close and read the adjustment journal line by line.
• Finish the official “fixed assets and inventory” path — 4 hours 56 minutes.
• Write inventory close into your close checklist, used in the next station.
• Revisit the inventory cycle for the general principle.

The three commonest mistakes

One: never running inventory close. The cost stays estimated forever, and pricing decisions rest on numbers that never settled.

Two: running it after the ledger period closes. Adjustments land in the following month and distort its margin.

Three: one costing method for the whole company. Chosen once and forgotten, so contradictory categories share one logic.

The acceptance test for this station

1. Distinguish the physical and financial update and say what decides whether the first posts.
2. Explain why an issue’s cost is an estimate all month.
3. Explain what inventory close does and its effect on margin.
4. State its place in the close order and why it cannot be reversed.
5. Show your exercise and the adjustment journal you predicted against what resulted.

What comes next

The numbers have settled. The next station turns them into statements: the close and reporting — the full close order, the settlements, and the three reporting layers.