A tax return is the report you file with the Internal Revenue Service every year to document your earnings, deductions and tax obligations. If you earn $400 in self-employment income or significant earned or investment income, you must file a tax return. Your declared allowances affect the information you report on your return.

Tax Return Basics

Tax returns are due April 15 every year, or the following Monday if the 15th is on a weekend. You can work with a tax firm or accountant to prepare your return or use an online software program to self-report your taxes. Using forms W-2 or 1099, deduction receipts and other tax documents, you must provide all income and deduction information, as well as details of any credits you wish to claim. Once you record all income, deductions and credits, you file your return and make a payment if you owe additional taxes.

Allowances and Withholdings

When you get a job, your employer usually has you complete a W-4 as part of orientation. This form asks you to provide your name, Social Security number and other personal details. You also use a worksheet to declare tax-deduction allowances. The allowance is a number based on your filing status, number of dependents and other circumstances that you expect to reduce your tax obligation. The more allowances you claim, the less your employer withholds from your paychecks.

W-2 and Reporting

By Jan. 31 of every year, your employer must provide a W-2 form that details your wages, withholdings and deductions for the previous year. The W-2 shows amounts withheld for federal and state tax obligations. These amounts are based on your income, tax bracket and allowances claimed. Generally, it is better to claim conservatively to avoiding owing more money when you file. If you do so, you're more likely to get a refund after your return is processed.

Deductions and Credits

When you prepare your return, your deductions and credits offset your tax obligation. You can take the standard IRS deduction for your filing status or itemize if you paid for things like mortgage interest or property taxes or made charitable contributions. Deductions reduce your taxable income and obligation. Credits actually reduce the amount you owe. The combination of deductions and credits reduces your tax burden. If you claim more than you projected when completing the W-4, you should get a refund when you file.