In this video I walk you through exactly how we track profitability for Kiwi Brick Exchange across BrickLink, BrickOwl, and TradeMe (our NZ version of eBay). I’m a big believer that if you’re selling LEGO for profit—whether it’s a side hustle or a proper business—you need a system that measures sales, cost of goods sold, and expenses, and you need it for tax purposes too. We use a Google Sheets “Profitability Tracker Master” that totals everything up for the year, then calculates gross profit, net profit, an estimated tax amount (I use 39% for my situation), and net profit after tax. I also show how we break results down month-by-month, because trends matter. We track KPIs like BrickLink rank, parts uploaded, lots, and order count, then link each month back into the master sheet so you only enter data once. I demo logging an order (platform, order ID, total, payment received, payment method), recording cost of goods (buying LEGO), and categorising expenses like packaging, postage, home office, petrol/transport, errors/refunds, equipment (like storage containers), and online tools. Finally, I explain why we keep a separate Orders tab for shipping status and checking if we’re charging the right shipping—flat rate for smaller orders, and free shipping over a threshold (currently $75) so it evens out over time.