Usually, the IRS is rather prompt in asking for additional money. You can contact the IRS by calling 800-829-1040 (Monday–Friday, 7:00 a.m.–7:00 p.m. your local time). When calling, have a copy of your return on hand because you’ll likely be asked questions about your entries (e.g., adjusted gross income; taxable income; tax due) to verify who you are.
Items directly reducing income. Personal deductions such as for mortgage interest, state and local taxes, and charitable contributions are allowed only if deductions are itemized on Schedule A, but deductions such as for alimony, capital losses, moving expenses to a new job location, business losses, student loan interest, and IRA and Keogh deductions are deducted from gross income even if itemized deductions are not claimed.