go back on (one's) promise

go back on (one's) promise

To not do something one said one would do; to renege on something. People are beginning to worry that the governor is going to go back on his promise and not lower taxes for lower-income families after all. You made a commitment to support our project, and now you've gone back on your promise! If the board goes back on their promise to fund our research, we can't possibly continue.

See also: back, go, on, promise

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