Generally, the more allowances, the less tax will be withheld from each paycheck. The fewer allowances claimed, the larger withholding amount, which may result in a refund.
If you need more help filling out your W-4, try using your withholding calculator. https://www.irs.gov/individuals/irs-withholding-calculator
(Note: Due to the tax law changes signed into law on December 22, 2017, the IRS withholding calculator is currently unavailable. ?The IRS will update the calculator as soon as updated withholding information is available).
