ITINs for Spouses and Dependents
If you want an ITIN because you're married to a US citizen who wants to file their US tax return electronically, bad news. The IRS doesn't accept this reason. Your US spouse needs to list you on their tax return and claim an "allowable tax benefit."
The rules changed in 2018. Since then, the IRS expanded its instructions (without changing the requirement that the ITIN applicant show a personal US-tax need).
Expanded IRS Instructions for Spouses and Dependents
In their words
Allowable tax benefit
For tax years after December 31, 2017, spouses and dependents are NOT eligible for an ITIN or to renew an ITIN unless they are claimed for an allowable tax benefit or they file their own tax return. Spouses and dependents must be listed on an attached U.S. federal tax return and include the schedule or form that applies to the allowable tax benefit. An allowable tax benefit includes a spouse filing a joint return, head of household (HOH), American opportunity tax credit (AOTC), premium tax credit (PTC), child and dependent care credit (CDCC), or credit for other dependents (ODC).
The magic words are: Filing a joint tax return means that you - the non-US spouse who wants an ITIN - are choosing to file a tax return with your spouse as if you're a US citizen (and declaring your world wide income to the IRS and filing an FBAR).
An alternative that may suit your needs is to create a US limited liability company, which is covered here. It's a big move to make your US citizen spouse happy. Worth it? That's up to you.
What if We're Married Filing Jointly?
A citizen of another country can get an ITIN when they choose to be treated as a US resident for tax purposes and file with their spouse. The original, signed tax return needs to accompany the ITIN application. You can't apply for the ITIN before filing, unless you can rely on a different IRS-approved reason.
Read more about the choice to file as if a US resident on the website from the IRS.
Can my spouse get an ITIN so I can e-file my taxes?