US taxes: the first year
Federal, state, FBAR and the treaty with the Netherlands. Enough to understand what's coming; then you hire someone.
Three layers of tax
Federal (IRS, 10–37%), the state of California (1–13.3%, among the highest in the US) and local sales tax on purchases. Your employer withholds income tax based on your W-4 form; fill it in carefully. You also pay Social Security (6.2%) and Medicare (1.45%). Net, you keep roughly 65–70% of a $100,000 salary in LA.
Filing a return
The tax year is the calendar year; file by April 15. Your employer sends a W-2 (annual statement) at the end of January. Simple situation (one employer, no foreign assets)? TurboTax or FreeTaxUSA. First year with Dutch income, a house or investments? Hire a CPA or enrolled agent with expat experience ($500–1,500).
Dual status and the treaty
In your moving year you're likely dual-status: part non-resident, part resident. The NL–US tax treaty prevents double taxation, but you have to apply it. Dutch state pension, a rented-out home in NL and box-3 assets each have their own rules. Deregister from your municipality: that makes you a non-resident taxpayer in NL.
FBAR and FATCA: your Dutch accounts
Did your foreign accounts (bank, savings, investments, sometimes pension) total more than $10,000 at any point in the year? Then file an FBAR with FinCEN (free, online, by April 15 with automatic extension to October). Penalties for forgetting are steep. At higher amounts, form 8938 (FATCA) is added.
US investment rules (PFIC) make Dutch investment funds tax-unfriendly. Discuss your Dutch portfolio before you move.