WordNet records no synonym and no antonym for budget. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a sum of money allocated for a particular purpose
“the laboratory runs on a budget of a million a year”
a summary of intended expenditures along with proposals for how to meet them
“the president submitted the annual budget to Congress”
Synonyms, antonyms and the broader and narrower relations for budget come from Princeton University’s WordNet. Full sources and licences.