From Longman Business Dictionary
overspendo·ver·spend /ˌoʊvəˈspendˌoʊvər-/ verb (past tensepst and past participlepp overspent /-ˈspent/) [intransitiveI] to spend more than you can afford or more than you intendedoverspend byHealth authorities, which overspent by more than £300 million last year, must balance their books this year.
—overspend /ˈəʊvəspendˈoʊvər-/ noun [countableC usually singular]They have moved from a £21 million surplus to a £6 million overspend.
—overspending noun [uncountableU]years of overspending on public programs