Upstream/downstream inventory profit elimination calculator

Compute and book intercompany inventory profit eliminations.

Inputs:
- IC inventory sales details: {ic_inventory_sales}  # seller, buyer, sales price, cost, markup, dates
- Ending inventory on hand from IC purchases: {ending_ic_inventory}
- Tax considerations (optional): {tax_considerations}
- Reporting period: {period_end_date}

Output:
1) Unrealized profit calculation by IC stream (upstream/downstream), including attribution logic.
2) Elimination journal entries (COGS/Inventory and related accounts) with memos.
3) Rollforward schedule for deferred profit (beginning, new deferrals, releases, ending).
4) Evidence checklist and control tips.

Be clear about assumptions for markup and units.