For individuals, estimated taxes for the third installment are due (Form 1040-ES). For calendar-year C-corporations, estimated taxes for the third installment are due (Form 1120-W).

For partnerships, file an income tax return (Form 1065 or Form 1065-B) and provide each partner with a copy of Schedule K1 (Form 1065). For S-corporations, file an income tax return (Form 1120-S) and provide each shareholder with a copy of Schedule K-1 (Form 1120S).

For calendar year trusts and estates, file an income tax return (Form 1041). Pay any income tax due.