Before you start

An SSN or ITIN
Form W-4 for federal withholding and California Form DE 4 for state withholding
Records of foreign income and foreign financial accounts
The property tax bill and any special assessments, if you own property

Step-by-step

1
Complete Form W-4 and California Form DE 4 on day one
Federal and California withholding are separate forms. Your payslip will show federal withholding, California withholding, Social Security, Medicare and State Disability Insurance — the last of which now applies to every dollar of wages with no ceiling.
Via employerWho: YouFirst week of employment
2
Determine your US tax residency
The substantial presence test counts weighted days across three years to decide whether the US taxes your worldwide income or only US-source income. Your visa category does not decide this.
OnlineWho: You
3
Check for an applicable tax treaty — and check California separately
The US has treaties with around 70 countries that can reduce or exempt tax on particular income. California does not conform to all federal treaty provisions, so income exempt federally can still be taxable by the state. This is a genuine trap for people arriving on a treaty position and it is worth professional advice rather than an assumption.
OnlineWho: You
4
Know the sales tax you are actually paying
California's rate varies by jurisdiction. The City of Sacramento is at 8.750% and the unincorporated county at 7.750%, which is meaningfully below most of the Bay Area. Groceries and prescription medicine are exempt; prepared food is not. Note the boundary matters — the rate changes when you cross into or out of the city.
OnlineWho: You
5
If you buy, understand Proposition 13 and check for Mello-Roos
Your taxable value is what you paid, rising about 2% a year until you sell — so budget from the purchase price, not from a neighbour's bill. Then check whether the property sits in a Mello-Roos community facilities district, which levies a special tax on top to fund infrastructure. These are widespread across Natomas, Elk Grove, Rancho Cordova and Folsom and can add a substantial annual sum.
OnlineWho: You
6
Check the flood control assessment on the parcel
Properties in the Sacramento Area Flood Control Agency's area pay an assessment toward levee and flood infrastructure, which appears on the property tax bill. It is specific to this valley and does not exist in the Bay Area comparison you may be making. Check the actual bill for the parcel rather than the headline tax rate.
OnlineWho: You
7
File your federal and California returns
The tax year is the calendar year. California's individual return is filed with the Franchise Tax Board, which offers a free CalFile option at lower incomes. California's deadline generally follows the federal one, but the state has its own extension rules — check the FTB's calendar.
OnlineWho: YouBy mid-April annually
8
File an FBAR if foreign accounts exceed $10,000
Aggregate foreign account balances over $10,000 at any point in the year trigger a FinCEN filing, separate from your tax return and with its own penalties.
OnlineWho: You

Documents you’ll need

Form W-2 from each employer, issued by 31 January
Form 1099s for freelance, interest and investment income
Forms W-4 and DE 4 filed with your employer
Passport and travel history for the substantial presence day count
Property tax bill, including any Mello-Roos and flood control assessments
Foreign account statements for FBAR reporting

Things most newcomers don’t know

Sacramento gets California's tax rates applied to valley prices, which is the whole argument for the city.

The 13.3% top rate, the uncapped SDI and Proposition 13's mechanics are identical to San José's — they are state law. What differs is the base. Sales tax is 8.750% here against 9%-plus across most of Santa Clara County, and Proposition 13 pins your property tax to a purchase price that in Sacramento is a fraction of a Bay Area one. The same tax code produces a very different bill.

Source: California Department of Tax and Fee Administration / California Franchise Tax Board

The SDI wage ceiling was removed in 2024, and high earners felt it.

State Disability Insurance used to stop at a wage cap. Since 2024 it applies to every dollar of wages, which functions as an additional percentage-point-ish levy on high salaries with no upper limit. Anyone modelling a California offer from a pre-2024 calculator is understating the deduction.

Source: California Employment Development Department

California does not conform to every federal tax treaty provision.

Income exempted from federal tax by a treaty can still be taxable by California. Newcomers arriving on a treaty position frequently assume the exemption flows through to the state return and discover otherwise a year later. It is the single most common state-level tax error among new arrivals from abroad here.

Source: California Franchise Tax Board

The flood control assessment is a Sacramento line that no Bay Area comparison includes.

Properties in the SAFCA area pay toward levee and flood infrastructure through the property tax bill. It is modest relative to the mortgage but it is real, it is specific to living behind levees, and it sits alongside a flood insurance requirement in mapped high-risk zones. When comparing a Sacramento purchase to a Bay Area one, both belong in the model.

Source: Sacramento Area Flood Control Agency

Common mistakes to avoid

Assuming a federal tax treaty exemption automatically applies to the California return.
Using a pre-2024 calculator and understating the uncapped SDI deduction.
Budgeting property tax from a neighbour's bill rather than from your own purchase price.
Buying in a Mello-Roos district without pricing the special tax.
Comparing a Sacramento purchase to a Bay Area one without the flood assessment and flood insurance in the model.
Missing the FBAR because a home-country account did not feel 'foreign'.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.