If you are filing as head of household with three dependents, you will not owe any federal income tax until your income is somewhere over $55,000 per year.*** So if you fill out the W-4 showing HOH and 3 dependents, you would not expect to have any federal withholding unless your gross taxable income was more than $1000 per week.
*** this is a rough calculation based on the following. $55,000 -$18,000 standard deduction equals $37,000. At 15% income tax, the tax due is $5550. You will get a $6000 tax credit for your three dependents, meaning you owe no federal income tax.
