Fulfill is the American spelling of the verb meaning to accomplish or to satisfy. Fulfil is the preferred spelling outside North America. Both forms are common in Canadian writing.
The spelling preferences extend to fulfilment and fulfillment, but not to fulfilled, fulfilling, and fulfiller, which have two l’s everywhere.
The question is, how do we fulfill that vision? [Wall Street Journal]
But he was forced to battle his insurance company of more than 50 years when it failed to fulfill its $220,000 policy. [Los Angeles Times]
Voters in 2008 would have seen he didn’t measure up then, had not millions been swept away with emotion and wish-fulfillment. [Denver Post]
Outside the U.S.
The Catholic Church is facing many problems, but here we will focus on an inability to fulfil its primary task … [Irish Times]
The book, she admits, has an unexpected touch of wish-fulfilment to it. [Guardian]
There is even a tenant who seems likely to fulfil that most essential of television roles: the character audiences love to hate. [Sydney Morning Herald]
This ngram graphs the use of fulfil and fulfill in British books published between 1800 and 2000:
And this ngram, which graphs the words’ use in American books from the same period, suggests that the transition from fulfil to fulfill occurred in the first half of the 20th century: