One method you can use is to increase your federal withholdings by completing new W-4 forms. When completing the W-4, complete Step 2 of the Form W-4 instructions to account for a working spouse. Underwithholding can occur if both spouses enter Married Filing Joint filing status in Step 1 and fail to complete Step 2. You can also enter an amounts to be withheld per pay period in Step 4(c) for additional withholdings.
Using the estimate you have given of owing 3-6K each year, you can determine the additional amount needed by diving it by the number of pay periods you are paid. For example, if you are paid Bi-Weekly (26 pay periods) and you want to have an additional $3K withheld per year, you can enter $116 ($3,000 / 26 - Rounded up) on line 4(c) of the W-4 form. You can each make these changes to your W-4 so you are able to increase the federal withholdings based on your income.
