While they sound the same, they have different meanings and spellings:
* Cut off: This is the past tense of the verb "to cut off," meaning to separate something or someone.
* Cutoff: This is a noun meaning a point at which something ends or is discontinued.
Examples:
* Cut off: "The phone line was cut off during the storm."
* Cutoff: "The cutoff time for registration is 5 pm."