go back on (something)

go back on (something)

To not do something one said one would do; to renege on something. People are beginning to worry that the president is going to go back on his promise of lowering taxes for lower-income families. You made a commitment to support our project, and now you've gone back on your word!
See also: back, on

go back on

Fail to honor or keep, as in You can't go back on your word, or One should never go back on a promise. [Mid-1800s]
See also: back, on