@kogi58 wrote:
The estimator doesn't tell you at all actually on how you have to adjust anything. It just estimates your return - I've done it and it's no help at all on how to fill the new W4 out. The question still is whether I have to claim him or me - simply because of his custody situation.
A step-parent has the same legal right to claim a child as a dependent as a biological parent, and the ability to claim the children just depends on the same usual factors that apply to the biological parent (where the children lived, how old they are, and if they supported themselves or not.)
Then, as long as you will be filing a joint married return, you and your spouse are essentially "one taxpayer" for most purposes. If the children lived in your home more than half the year, you can claim them as dependents on your joint return.
Because you will file a joint return, you need to coordinate your W-4s and whenever you submit one to a new job, you need to review them all and sometimes submit new forms to all your jobs. If you don't like the online calculator, use the worksheets on the W-4 itself; the whole form is 4 pages including instructions and worksheets, even though the employer only needs page 1 with the signature.
Where the instructions say that the withholding will usually be more accurate if the dependent adjustments are made on the job with the higher income, it's perfectly fine if that is you, because you are a legal parent under the tax law and will presumably be filing a joint return.
