How in the world could you possibly take an $86k salary down to $0 taxes. That blows me away.
Here's how:
Start by taking off FICA taxes and then 5% for the 401(k) (yeah, I'd like to contribute more, but we're kinda tight right now, for reasons that will soon become evident)
Deductions: between mortgage insurance and property taxes, that's close to $15k (that's why I can't contribute more to my 401(k)!). Another $9k in charitable contributions, and a few thousand more for state income or sales taxes, car mileage when volunteering, etc.
Exemptions: last year we had 5 kids on our tax return, so 7 exemptions for another $27,300 reduction in taxable income.
Taxable income: now about $27k, so taxes are around $2700.
Child tax credit: wipes out the $2700 tax liability
Additional tax credit: gives us the excess Child Tax Credit ($2300) back.
Heck, had we only had 3 kids at the time, we still woulda been about $0 for tax liability. This year's taxes will be even further in the hole--we had our six child! :D