Brut non-vintage champagne (aka Brut NV), or simply Brut champagne, is the most common and most sold type of champagne. It is called brut sans année (BSA) in French. It is the result of a combination of wines from different years, and usually from many crus.
Non-vintage champagne must be kept sur latte (bottled and flat) in the cellar for at least 15 months (of which 12 months on lees before disgorgement), but virtually all major Champagne houses keep them much longer, two to three years or more.
The most sold brut non-vintage champagne is Moët & Chandon Burt Impérial, followed by Veuve Clicquot Yellow Label.
Note that some prefer to call this category of champagne multi-vintage (MV), a more noble reading of the same concept. However, some argue that MV should be used only if the actual vintages used were great or solid. I am in between and use both terms, depending on the philosophy of the winemaker on the subject.
BSA are my favorite champagnes because they include an intense work of creation (when properly crafted). They are considered the business card of any house, showing its craftsmanship, and embedding its style. Note that even if they are the entry-level wine of virtually all Champagne houses, you also have top-end champagnes made this way.
The greatest example to me is Krug Grand Cuvée, my current favorite champagne. Among more affordable brut non-vintage champagnes, Louis Roederer Brut Premier is one of the most praised. Some of my favorites are Gosset Grande Réserve, Deutz Brut Classic, Bruno Paillard Première Cuvée, Pol Roger Brut Réserve, Bollinger Brut Special Cuvée, Charles Heidsieck Brut Réserve but increasingly also Philipponnat Royale Réserve, Barons de Rothschild Brut, Ayala Brut Major, and many more that buy and drink regularly. The beauty is that they have such different styles that I can choose according to my mood, the dish I am eating, or my curiosity as any time I drink the sane champagne, it’s a rediscovery for me.