We don't have synonyms for tax day yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are tag day.
(n) :
(US, colloquial) The day on which individual income tax returns are due to be submitted to the federal government, or within an individual state.
(n) :
(US, colloquial) Ellipsis of Tax Freedom Day. [The first day of the year on which a nation as a whole has theoretically earned enough income to pay its taxes.]
(n) :
(US, colloquial) The day on which individual income tax returns are due to be submitted to the federal government, or within an individual state.
(n) :
(US, colloquial) Ellipsis of Tax Freedom Day. [The first day of the year on which a nation as a whole has theoretically earned enough income to pay its taxes.]