How to spell 40 40 is spelled forty in English. Hear it & practice → On a check To write $40.00 on a check, the words line reads: Forty and 00/100 Full check-writing guide → Related numbers4 four 50 fifty 1 one 10 ten 100 one hundred 1,000 one thousand Spelling guidesMoney amountsHow to write dollars in words.Writing a checkStep-by-step for US checks.Ordinals (1st, 2nd…)First, second, third, and beyond.All guidesDates, phones, fractions, decimals… ← 39All numbers41 →