>>>You have one item, or one item per size - that's up to the end user
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>>The concept here is, there is an item, it has multiple sizes (read packings), each size has multiple batches. So there is a stock at batch level, size level (ie. all batches stock) and at item level (total of the sizes), per se it is the same item at any stage because this is the real stock
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>OK so then you may have two levels of lookups - item, item's sizes - and a few properties to each of them (I guess the chemistry is the same, if physics isn't). Your inventory unit is still the batch - which may be your third level of lookup, because the expiry date, and maybe some attached paperwork (possibly certificate IDs etc, who knows what stool they may invent) with it. You only need to know which properties go to which level. Your inventory needs to know where things are and how many of them there are. Your thing is a box of pills of certain size AND batch - anything inside the batch has the same properties, right? So for one batch, you only need to know how many of it is where - in which location, which phase of the process etc, but that's transaction. Your SKU is the PK of the batch.

Yes thanks, the expiry date attachment to the batch is correct, so I will scratch what I mentioned to Srdjan, it has to go into a separate master / lookup table. Now my only problem is how it goes down with them, to go into this batch master data-entry form, select the item and it's packing and other particulars like exipry, save the batch and use it in production slip. Thanks I know what I am supposed to ask them now.