Before you start

An SSN or ITIN
Form W-4 with your employer for federal withholding, and SC W-4 for state withholding
Records of foreign income and foreign financial accounts
A legal residence application with the county assessor, if you own and occupy a home here

Step-by-step

1
Complete the W-4 and the SC W-4 on day one
South Carolina has its own withholding certificate alongside the federal W-4. With the 2026 rate change and the shift to federal AGI as the starting point, the state calculation is not the one last year's tables produced — check the withholding rather than assuming it carried over.
Via employerWho: YouFirst week of employment
2
Determine your US tax residency
The substantial presence test counts weighted days over 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
The US has treaties with around 70 countries that can reduce or exempt tax on particular income. Note that South Carolina now starts from federal adjusted gross income rather than federal taxable income, which changes how some federal adjustments flow through to the state return.
OnlineWho: You
4
File federal and South Carolina returns by 15 April
The tax year is the calendar year and both returns are due on the same date. The 2026 return — the first under the new rate structure — is due 15 April 2027.
OnlineWho: YouBy 15 April annually
5
If you buy a home, file the legal residence application immediately
The 4% assessment ratio for an owner-occupied primary residence is granted on application to the county assessor, not automatically. Charleston County's deadline is normally 15 January. It is worth doing on the day you close, because the alternative ratio is 6% and the 4% ratio also carries an exemption from school operating millage.
In personWho: YouBy 15 January
6
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 and additional to your tax return.
OnlineWho: You

Documents you’ll need

Form W-2 from each employer, issued by 31 January
Form 1099s for freelance, interest and investment income
Passport and travel history for the substantial presence day count
Deed, SC driver's licence and vehicle registration for the legal residence application
Foreign account statements for FBAR reporting

Things most newcomers don’t know

The income tax you researched last year is not the one you will pay.

H.4216 was signed on 30 March 2026 and applies from the 2026 tax year. It replaces the graduated schedule that topped out at 6% with 1.99% under $30,000 and 5.21% less $966 above it, and — the part almost nobody notices — it decouples South Carolina from federal standard and itemised deductions and makes federal adjusted gross income the state's starting point. Two people with identical gross pay can now land differently depending on how their federal deductions worked.

Source: SCDOR — information about H.4216

The 4% legal residence ratio is an application, not a status.

South Carolina's constitution sets 4% for an owner-occupied primary residence and 6% for a second home, a rental or other real property — and the 4% ratio carries an exemption from school operating millage on top. It is granted only when you apply to the county assessor and prove it, with a Charleston County deadline of around 15 January. People who buy in November and file in February pay a year at 6% on a house they live in.

Source: SC Department of Revenue — individual property tax (SCTIED Chapter 5)

Nine per cent sales tax, three points above the state rate.

The state rate is 6%. Charleston County adds Local Option, Transportation and Education Capital Improvement taxes to reach 9%, which is at the top of the South Carolina range — Beaufort and Greenville are at 6%. On a big purchase the difference between counties in this metro is real, and the SCDOR publishes the designation county by county.

Source: SCDOR — local tax designation by county (ST-500)

The hurricane deductible has its own tax-free savings account.

South Carolina's Omnibus Coastal Property Insurance Act created catastrophe savings accounts: money set aside in a designated interest-bearing account for a hurricane, flood or windstorm deductible, with the contributions and the interest exempt from state income tax. It reduces no federal liability, and withdrawals for anything else are taxed as ordinary income plus an additional 2.5%. Almost no newcomer knows it exists and on this coast it is directly useful.

Source: SC Department of Insurance — 2024 coastal property insurance market report

Common mistakes to avoid

Budgeting against the old 6% top rate, which no longer applies from the 2026 tax year.
Assuming the 4% owner-occupied assessment ratio is automatic. It is an application with a deadline.
Comparing counties on the 6% state sales tax and meeting 9% at a Charleston till.
Forgetting the annual county property tax on the car until the registration is blocked.
Assuming your visa type settles your tax residency.
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.