US/UK Cross-Border Tax
Advisors in New York
US and UK tax for British nationals living in the US and UK companies expanding into the American market, from our New York office.
The UK Answer Inside the US System
New York is the natural landing point for British professionals and UK businesses entering America, and it is where the two tax systems clash most. A Briton on assignment in Manhattan picks up US and New York filing obligations while their UK affairs (ISAs, pensions, property, company shares) carry on under HMRC's rules, several of which the US treats with suspicion. Our New York team knows both rulebooks: substantial presence and treaty tie-breakers on arrival, the US treatment of UK pensions and investment wrappers, state and city residency on top of the federal picture, and the entity, withholding, and transfer-pricing structure a UK company needs before its first American hire or invoice.
A UK SaaS Company's American Build-Out
Case Study: New York Cross-Border Engagement
A profitable UK software company won its first major US customers and needed a New York presence: salespeople on the ground, dollar invoicing, and eventually a US entity, all without triggering avoidable tax on either side.
Formed a Delaware C-corporation subsidiary registered in New York, with an intercompany services agreement pricing the US entity's functions at arm's length and containing the permanent establishment risk under Article 5 of the treaty.
Completed Form W-8BEN-E with treaty claims for the UK parent's remaining direct contracts, reducing US withholding on cross-border payments to the treaty rate.
Built the compliance calendar across both systems: Forms 1120 and 5472 in the US, transfer pricing documentation, and the UK corporation tax and PAYE consequences of seconding two founders to New York.
$310K
First-Year Withholding and Double-Tax Exposure Avoided
Cross-Border Technical Work
Arrival Planning: Substantial Presence and Treaty Tie-Breakers
The transition from UK resident to US taxpayer is the best planning window a Briton in New York will ever have.
US residency arrives by green card or by the substantial presence test's weighted 183-day formula, and once resident, worldwide income and worldwide reporting follow. Before that line is crossed, we act. We realise gains while the client is still outside US jurisdiction, review ISAs and UK funds that become PFIC problems on day one, evaluate closer-connection claims and Article 4 treaty tie-breakers for split years, and run the UK Statutory Residence Test's split-year provisions in parallel so departure from HMRC and arrival at the IRS line up instead of overlapping.
FIRPTA and UK Investors in US Real Estate
Section 1445 withholding, Form 8288-B relief, and the estate tax trap behind US property.
When a non-resident Briton sells US real estate, FIRPTA requires the buyer to withhold up to 15% of the gross price, often far more than the actual tax on the gain. We file Form 8288-B withholding certificates to reduce or eliminate the withholding before closing, and prepare the 1040-NR that reconciles the true liability. There is a quieter danger too: US-situs assets above $60,000 expose non-resident non-citizens to US estate tax at up to 40%, a risk the US/UK estate tax treaty and pre-acquisition structuring can substantially reduce.
New York State and City Residency for the Cross-Border Client
The federal return is only half the picture. New York layers its own residency regime on top.
New York taxes residents on worldwide income and enforces its position through statutory residency: 183 days plus a permanent place of abode makes you a resident even if your domicile is London. City residency adds a further levy. New York also does not honour federal treaty tie-breakers, so a Briton who is a UK treaty resident federally can still be a full New York resident. We manage day counts, abode analysis, and allocation of UK income, and we plan departures for assignees heading home so trailing New York exposure ends cleanly.
Common Questions in New York
I am British and moving to New York. What happens to my ISA and UK investments?
The ISA wrapper means nothing to the IRS. Once you are a US tax resident, ISA income and gains are US-taxable, and most UK funds inside an ISA are PFICs facing punitive US tax treatment and Form 8621 reporting. The best window to act is before you trigger US residency, because restructuring or realising positions pre-arrival is far cheaper than unwinding them afterwards. UK accounts also become reportable on FBAR and Form 8938.
Our UK company wants to hire in the US. Do we need an American entity?
Not always, but usually. Hiring employees, closing contracts, or holding inventory in the US can create a permanent establishment that drags the UK company's profits into US corporate tax. A Delaware subsidiary with an arm's-length intercompany agreement typically contains that risk, enables US payroll and benefits, and simplifies customer contracting. The alternative, an employer-of-record, works for an initial hire but scales poorly. The right answer depends on headcount, contract flow, and treaty position.
What is the difference between a W-8 and a W-9, and which do I give?
A W-9 certifies you are a US person (citizen, green card holder, or US entity), so no withholding applies. A W-8BEN (individuals) or W-8BEN-E (entities) certifies foreign status and claims treaty benefits, typically reducing the default 30% US withholding on cross-border payments. Giving the wrong form either triggers unnecessary withholding or misstates your status. Your correct form can change in the year you become or cease to be a US resident, a transition we manage routinely.
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