In Commander, does your commander's mana value in the command zone include commander tax?

A card's mana value (formerly called converted mana cost) is calculated from its printed mana cost only, as defined in CR 202.3. Commander tax — the additional {2} per previous cast — is an additional cost to cast the spell, not part of the mana cost printed on the card.

CR 903.8 specifies that the commander tax is an additional cost, applied when you cast your commander from the command zone. Additional costs do not change a spell's mana cost or mana value (CR 601.2b, 202.3a). The mana value of your commander remains fixed at what its printed mana cost calculates to, regardless of how many times it has been cast.

This matters in several practical situations: effects that check mana value (like Trinisphere or cascade triggers), cost-reduction effects, or cards that reference a spell's mana value on the stack will all use the printed mana cost value, not the inflated amount you actually paid.

Concrete example: Your commander is Ur-Dragon (mana cost {4}{W}{U}{B}{R}{G}, mana value 9). You've cast it twice before, so the commander tax adds {4}. You pay {8}{W}{U}{B}{R}{G} total, but Ur-Dragon's mana value on the stack is still 9, not 13. A Mystic Snake trying to counter it would cost {2}{G}{U} — not more — regardless of how much you paid.

In the command zone, a card has no mana value derived from being a permanent or spell, but CR 202.3b clarifies that a card's mana value in any zone where it has a mana cost is simply that printed mana cost's value. Commander tax never factors in.