My wife got a $12000 enlistment bonus last year.It was taxed before she got it,She netted $9000.
Her income on her w2 was $9000 more than usual wich put us in a higher tax braket and gave us less than usual on our return.
Did we get double taxed,or should i say overtaxed.It seems like if we had already been taxed on the $12000 bonus it wouldn't be taxed again when we file.
what am i missing here?

A bonus is considered income if it's not in a combat zone.

The tax is withheld when the bonus is paid. When you file your return, the bonus is included in the total income. As such your income is greater than normal. You where taxed once. Your return is a reconciliation of your income, deductions, taxes paid and taxes owed. The net result is the amount your pay or receive in a return.

The US has a marginal rate tax system. That means that the first certain amount of income is taxed at a percentage. I believe that is currently 10%. Then next amount of income s taxed at a higher percentage, again I believe that is 15%. So only the extra income is taxed at a higher rate.

Also remember while it might seem your income was only $9K higher, some of the income you might be thinking about is not counted. Allowances like Family Separation, BAH, BAS are excluded in the income as they are allowances and are non taxable.

I understand allowances and combat zone aren't taxeable.I was just trying to wrap my head around the bonus being taxed in advance then our tax bracket going up and getting taxed at a higher rate.It seemed like a double tax.I think i get it now,thank you.

The US uses a marginal tax system. Some income is taxed at 10%, then next range at 15%, the next range at 25% and so on. That is after you take off deduction and exemptions, which makes the first $8,750 tax free or 0% tax rate. If you are married filing jointly you double this amount. Children add to the tax free amount, and if you itemize, you get a bigger amount tax free.

Single Filing Status
(Tax Rate Schedule X)

* 10% on income between $0 and $8,025
* 15% on the income between $8,025 and $32,550; plus $802.50
* 25% on the income between $32,550 and $78,850; plus $4,481.25
* 28% on the income between $78,850 and $164,550; plus $16,056.25
* 33% on the income between $164,550 and $357,700; plus $40,052.25
* 35% on the income over $357,700; plus $103,791.75

Married Filing Jointly or Qualifying Widow(er) Filing Status
(Tax Rate Schedule Y-1)

* 10% on the income between $0 and $16,050
* 15% on the income between $16,050 and $65,100; plus $1,605.00
* 25% on the income between $65,100 and $131,450; plus $8,962.50
* 28% on the income between $131,450 and $200,300; plus $25,550.00
* 33% on the income between $200,300 and $357,700; plus $44,828.00
* 35% on the income over $357,700; plus $96,770.00