Should we expect to pay $3318 more in taxes than I did last year when our taxable income was only $1200 more?

Nothing is the same as last year.  There are many differences.   If you have kids they are a year older.  That can make big changes.  Also the tax laws and brackets might have changed.  The withholding tables change each year.   Each year is separate.  

You have to print out and compare this year with last year’s return LINE BY LINE and see what changed.  Maybe you’ll spot something you left out or entered wrong.  Common things are leaving a decimal point out or typing a comma for a decimal point, or typing an extra digit.  Getting the wrong taxable amount on a 1099R entry or entering the 1099R wrong and getting hit with a penalty.  Missing the qualified dividends in 1099-DIV box 2a.   I could go on and on.   

I suggest you com[pare last year to this years tax return.

From the left sidebar

1. Select Tax tools

• You may have to minimize both the Federal and State options by clicking the Down Arrows on the Sidebar.
• You will then clearly see Tax Tools
• Click the arrow to up to see additional options

1. Click Tools
2. A Menu will pop up
3. Select View tax summary
4. On the left panel click Preview my 1040

Some Key numbers to compare:

• 11 Adjusted Gross Income
• 12 Deductions
• 15 Taxable income
• 16 Tax
• 19 Child Tax Credit
• 26 Earned Income Tax Credit
• 28 Additional Child Tax Credit
• 33 Total Payments
• 34 Overpayment
• 35a Refund
• 37 Amount you owe