An EIN for a UK company is the thing your American customer will not stop asking about. They have held the invoice for three weeks now. Their accounts team keeps forwarding the same sentence about a nine-digit number. Meanwhile the W-8BEN-E sitting on their desk already contains the answer, on a line almost nobody reads.
Line 9b asks for a foreign tax identifying number. Enter your company's UTR there and, for most treaty claims, the demand for an American number simply stops applying. The instructions say so in one sentence, which is precisely why it gets missed.
That matters because the alternative costs real time. The IRS shuts its online application to companies with no US presence, so a British applicant falls back on an international telephone line, a fax machine, or four weeks of post.
None of which is wasted effort if you genuinely need the number. Hiring in America, running US payroll, or sitting as a partner in a US trade or business all require one, whatever line 9b happens to say.
So this guide answers the two questions in order. First, whether you need an EIN at all. Second, how a company outside America actually gets one when the answer turns out to be yes.
When the treaty claim needs no EIN at all
The W-8BEN-E instructions require a US taxpayer number where you claim treaty benefits and have not given a foreign tax number on line 9b. Read that the other way round. Supply your UK reference on line 9b and the requirement generally falls away.
That single line resolves most of the cases which reach us. A British company holding a UTR already has a foreign tax number, so it can complete the form without ever approaching the IRS. Our guide to the W-8BEN-E walks through the rest of it.
The instructions also list income types needing no US number even without line 9b. Dividends and interest on actively traded stocks and debt sit there, alongside dividends from registered mutual funds.
What is an EIN for a UK company?
An EIN is a nine-digit employer identification number, and it serves as a US taxpayer identification number for an entity. The W-8BEN-E instructions put it in exactly those terms. It identifies your company to the IRS much as a UTR identifies it to HMRC.
The name misleads almost everybody. You need no employees, no payroll and no American office to hold one. Plenty of British companies carry an EIN purely because a form once demanded it.
When you genuinely must have one
Three situations force the issue. A partner in a partnership carrying on a US trade or business must file an American return, so it needs a number. Certain annuity exemptions require one. And a treaty claim with no foreign number on line 9b requires one too.
Beyond the W-8BEN-E, ordinary American obligations bring their own. Hiring staff in the States, opening a US bank account, or filing a protective return all need the company identified to the IRS first.
What an EIN is not
An EIN does not make your company American. It creates no filing obligation by itself, and it does not mean the IRS expects a return next spring. Many British companies hold one and file nothing at all.
Still, it protects you from nothing either. Holding a number changes nothing about whether your profits count as effectively connected income, which turns on what you actually do in America.
Why your customer insists anyway
The payer carries the risk, which explains the pressure. A US business that under-withholds owes the tax out of its own pocket, so its finance team asks for every document it can think of, including ones the rules never required.
So show them line 9b. In our experience a short note pointing at the instruction settles it faster than an argument does, and it costs nothing to try before you apply. The withholding they fear lands on Form 1042-S either way.
Why the online application refuses you
The IRS restricts its online service to applicants with a legal residence, principal place of business, or principal office or agency in the United States or its territories. A British company with none of those cannot use it, and the instructions say so plainly.
The service also requires the principal officer to hold a valid SSN, EIN or ITIN. So two separate conditions block the typical UK applicant, and neither produces a helpful message on screen.
How does a British company actually apply?
Three routes stay open: telephone, fax and post. The IRS reserves the telephone route for international applicants only, which for once works in your favour. Complete Form SS-4 before you use any of them.
Use one method only. The instructions warn that applying twice produces two numbers for one entity, and untangling that costs far more than the original wait ever would.
- Download Form SS-4 and complete it in full before contacting anybody.
- Name a responsible party who is a natural person, never another company.
- Enter that person's SSN or ITIN, or write foreign where they can obtain neither.
- Pick one reason for applying on line 10, because a selection is compulsory.
- Choose a single route: telephone for speed, fax for a few days, post for a month.
- Write the number the IRS gives you onto your copy, then sign, date and keep it.
Applying by telephone
International applicants may call 267-941-1099, which is not a toll-free number. The line runs from 6am to 11pm Eastern time, Monday to Friday, so a British caller wants the afternoon or the evening.
The caller must hold authority to receive the number and answer questions about the form. Keep the completed SS-4 in front of you, because the representative works through it line by line.
Applying by fax or post
Fax usually returns an EIN within about four business days, and the line accepts documents at any hour. Applicants outside America use 304-707-9471, while 855-215-1627 serves anybody sending from inside the country.
Post runs to roughly four weeks, addressed to the EIN International Operation in Cincinnati. The instructions suggest allowing four to five weeks, so treat it as the route of last resort.
Two details catch people out every time. Give your own fax number on the form, since that is where the IRS sends the result back. And those particular lines accept nothing except EIN applications.
Comparing the three open routes
The table sets the routes against each other. Notice that the online option appears only to show why it will not help you.
Speed usually decides the choice. Still, a company facing no urgent deadline loses very little by faxing, and the paper trail suits some boards better than a telephone call does.
| Route | Who may use it | Typical wait |
|---|---|---|
| Online | Only applicants based in the US or its territories | Immediate, but closed to you |
| Telephone | International applicants only | During the call itself |
| Fax | Anyone, using the international number from abroad | About four business days |
| Post | Anyone, via EIN International Operation | About four weeks |
Who counts as the responsible party?
The IRS defines the responsible party as the person who ultimately owns or controls the entity, or who exercises ultimate effective control over it. The test looks at practical control of funds and assets rather than at a job title.
Crucially, that person must be an individual rather than a company. So a British subsidiary cannot name its parent, however neatly that would fit the group chart.
What if nobody has a US tax number?
This stops more applications than any other line on the form. It asks for the responsible party's SSN or ITIN, and most British directors hold neither. Still, the instructions answer the problem directly.
Write foreign on line 7b where the person has no SSN or ITIN and cannot obtain one. An entry on that line is compulsory, so leaving it empty sends the form straight back.
The one-a-day limit
The IRS issues one EIN per responsible party per day, and that ceiling applies across every route. So a director setting up several American entities at once cannot finish the job in an afternoon.
Plan the order instead. Groups restructuring across a weekend often discover this rule on the Monday, which is usually far too late to help them.
One number per entity, never per group
The instructions stay firm on this point. Each corporation within an affiliated group must hold its own EIN, so a British parent cannot share its number with an American subsidiary. Neither can two subsidiaries quietly share one between them.
So a group opening three US entities needs three applications, spread across three days because of the one-a-day ceiling. Build that into the timetable before anybody promises a launch date.
What if the number has not arrived in time?
Write Applied For, together with the date you applied, in the space where the number belongs. The instructions permit exactly that, so a slow application need not delay a return.
Never substitute a personal social security number for a company EIN. That creates a mismatch in the IRS records which outlives the original problem by years.
You can also ring 800-829-4933 to verify a number, or to ask what became of a posted application. Keep the date you sent it, because that is the first thing the IRS asks for.
Keeping the record current
A change of responsible party goes to the IRS on Form 8822-B, and the rules allow 60 days. Address changes travel on the same form, so one filing often covers both.
In our practice this is the forgotten step. A director resigns, nobody files anything, and three years later the IRS writes to somebody who left the company long ago.
An illustrative example
Take an illustrative case. A Manchester software company invoices an American customer, who withholds pending a W-8BEN-E and insists the form needs an EIN before anybody gets paid.
The company holds a UTR. So it enters that on line 9b as its foreign tax number, leaves the EIN box empty, and the treaty claim stands. No application follows at all.
Had the same company instead hired an employee in Texas, the answer would flip completely. Payroll obligations need the company identified to the IRS, so an SS-4 would go off by fax that same week.
Common mistakes we see
The commonest is applying before checking whether line 9b already solves it. The second is naming a parent company as the responsible party, which the form simply does not allow.
After those comes the duplicate application, usually created by a company that faxed, heard nothing, and then telephoned as well. Two numbers for one entity take months to merge, so pick a route and wait.
How US UK Tax Hub helps with an EIN for a UK company
First we work out whether you need the number at all, because that answer alone often ends the matter. Where you do, we complete the SS-4 and pick the route that fits your deadline.
We also keep the responsible party record straight afterwards. Start with our treaty relief service, or send the customer's request through our contact page and we will tell you what it genuinely requires.
