“NONTAX” is a valid word. — 13 points Scrabble

notnegation of a word or group of words
taxcharge against a citizen's person or property or activity for the support of government
tona United States unit of weight equivalent to 2000 pounds
tana browning of the skin resulting from exposure to the rays of the sun
antsocial insect living in organized colonies; characteristically the males and fertile queen have wings during breeding season; wingless sterile females are the workers
nanyour grandmother
taoan adherent of any branch of Taoism
oatannual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')

to
onin operation or operational
noa negative
ata highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium
anan associate degree in nursing
naa silvery soft waxy metallic element of the alkali metal group; occurs abundantly in natural compounds (especially in salt water); burns with a yellow flame and reacts violently in water; occurs in sea water and in the mineral halite (rock salt)
taa hard grey lustrous metallic element that is highly resistant to corrosion; occurs in niobite and fergusonite and tantalite
oxan adult castrated bull of the genus Bos; especially Bos taurus
axan edge tool with a heavy bladed head mounted across a handle

NONTAX