The typical starting point
The Shopify export, the Amazon export and a manually updated warehouse sheet never agree. Finance spends days each week working out what is actually in stock, while some SKUs run out and others sit unsold.
How I would build it
I would build a single Power Query pipeline that reads all three sources into one inventory table. An SKU master holds cost, price, lead time and safety stock. A reorder point calculator flags every SKU below threshold, a dead-stock report lists anything unsold for 90+ days, and a small VBA macro emails a weekly working-capital summary.
What it is designed to deliver
The founder gets one stock number they can trust, a weekly list of what to reorder and what is not moving, and finance stops reconciling channels by hand.