EBITDA is earnings before interest, tax, depreciation and amortisation: what the business earned from trading before financing and accounting effects. In an ecommerce P&L it is the third contribution margin minus overhead, and for most owner-run stores it is close enough to 'the profit' to be used that way daily.
In nouz it is CM3 minus overhead: everything the store made, minus every cost it carries, with recurring costs spread across the days they belong to rather than landing whole on the day the invoice arrived.
It is not a tax figure and it is not your annual accounts, which go on to charge depreciation and report earnings before interest and tax. It is the operating number, available the same day, and its job is to answer one question at breakfast: did yesterday pay?
Because it sits at the bottom of the ladder, EBITDA is where every mistake above it collects. A missing unit cost, an unpriced shipping zone or a retainer counted in the wrong line all land here, which is why the lines above it exist: a wrong bottom line is only fixable when you can see which step broke. How one example store's gross revenue thinned out on its way to EBITDA is traced in where the margin went. The contribution margin calculator walks the same ladder with your own numbers.
