Item

Because a business needs to say exactly what it bought, sold or holds, in a way that means the same thing to the warehouse, the accountant and the customer.

The item master is where the business's catalogue meets its inventory and its accounts. Its structure decides what questions can be answered — margin by category, stock by location, movement by variant — because reporting can only slice along the lines the master already draws. Deciding what constitutes one item is the highest-leverage and least-glamorous decision in an implementation.

• An item code is unique and permanent. Reusing a retired code makes every historical report about that code ambiguous.
• An item is either stocked or it is not, and that decision determines whether it has a stock ledger at all.
• Unit of measure is intrinsic to the item. Changing it after transactions exist invalidates every quantity previously recorded.

Items get created ad hoc by whoever needs one, and the same physical thing acquires three codes with slightly different descriptions. Stock splits across them, reordering fires on one while another sits idle, and the fix is not a merge script but a rule about who is allowed to create an item and what they must check first.

• Items that are sometimes stocked and sometimes drop-shipped, where the same code has a stock ledger for one flow and not the other.
• Batch- or serial-tracked items, where identity is per-unit rather than per-code and quantity alone is insufficient.
• Service items with no stock at all, which still need pricing, tax treatment and an HSN/SAC code.
• Items whose specification changes while the code stays — a supplier reformulation that nobody records is invisible until a customer notices.