First question time!

As is usually the case, I have read the IRS information on this subject and managed to confuse myself.

For 2016's tax return, using an Accountant, they prepared my filing as a non-resident due to the partial year (having moved in September). On that basis, I didn't need to get my two children ITIN's (knowing they cannot have a SSN - L2 Dependents), but I will do for 2017 given I will be filing as a Resident for this year. My last reading was that the ITIN needs to be applied for when filing the return, but I also read the website once and thought it didn't matter when you get this done.

Anyone know the right answer?

Despite being a numbers person, taxation rules appear to be my Kryptonite.

My understanding is that it can only be applied for with the tax return. But I'm definitely no specialist on the topic.

Rene

you can apply for it before doing the tax return - if you are claiming the kids/spouse as dependants on the tax return.
https://www.irs.gov/individuals/how-...ly-for-an-itin

you need to fill in the form W7 and either send off the documents proving US status and residency or go to a local office with the documents.

https://www.irs.gov/forms-pubs/about-form-w7

The link also states:
When should I apply?
You can apply for an ITIN any time during the year when you have a filing or reporting requirement. At a minimum, you should complete Form W-7 when you are ready to file your federal income tax return by the return’s prescribed due date. If the tax return you attach to Form W-7 is filed after the return's due date, you may owe interest and/or penalties.

My experience:
I completed the W7s and prepared my tax return. I then made an appointment at the IRS for the whole family to be processed. They completed the checks on the ID documents, filed the W7 and tax return together. They then process the W7, add the ITIN details to your tax return which is then processed. Do not leave it too late as the extra processing of the W7 delays filing of the return.

This way I was not sending passports to the IRS with no idea how long it would take to get things returned (if they were not lost in the meantime).

Philadelphia requires that you make an appointment, I am not sure if all locations do.