Hello
I am an engineer on worker visa (h1b) I changed jobs last year
And since my previous employer already started my green card process I had to reimburse them (that was on my offer sheet, so no ill will) so I paid them back $4000, can I claim this as a deduction? By the way that employer was CA based and I moved to WA with new employer

Also I heard some people claim there sales tax? I live in WA, can I do that?

You can deduct legal fees related to getting or keeping your job, subject to the 2% limit. Do you have any documentation that the $4K you reimbursed your former employer is a legal fee?

As for deducting sales tax - you have the option of deducting either state income tax or sales tax, but not both. Washington State does not have an income tax, so it makes sense for people there to deduct sales tax on their federal return. But in your case, since you moved in from a high tax state mid-year, you may be better off deducting the income tax you paid CA instead of sales tax - deduct whichever is greater.