Cross-Border Corporate Tax for UK and Overseas Groups
Written and reviewed by the International Tax Accountants editorial team. Last reviewed 29 July 2026.
Once a company trades across a border, its corporation tax stops being a single-country exercise. A foreign branch, an overseas subsidiary, or a treaty position sits behind the numbers, and each of those has to be identified, tracked and reported year on year rather than resolved once.
We take that work on as a standing engagement. We look at where the company is resident, whether it has created a taxable presence abroad or brought one into the United Kingdom, and how relief for foreign tax feeds through to the return. Then we file it.
This is the doing, not the explaining. If you want the underlying rule set out, our permanent establishment guide and the note on withholding tax on cross-border payments cover the mechanics. This page is what we are engaged to do about them.
What the Corporate Tax Engagement Covers
The engagement runs across the recurring cross-border points on a corporation tax return. We assess corporate residence, since a company incorporated in the United Kingdom is UK resident under CTA 2009 s14, while an overseas-incorporated company can still be caught by the central management and control test where its real decisions are taken here.
We test whether a permanent establishment exists under CTA 2010 s1141, whether a foreign branch or subsidiary changes the UK charge, and how controlled foreign company exposure and treaty relief affect the final figure. We then prepare and file the CT600 that reflects all of it.
Because profits crossing the marginal relief band change the effective rate, we also model whether the company falls in the small profits, marginal or main rate range before we file, using the HMRC method for corporation tax marginal relief.
Where Cross-Border Corporate Tax Gets Awkward
The friction is almost always dual residence and taxable presence. A company can be resident in two countries at once, which the treaty tie-breaker then has to resolve, traditionally by reference to the place of effective management. Getting that wrong exposes the same profits to tax twice.
Permanent establishment is the other pinch point. A dependent agent, a fixed place of business, or a long construction project abroad can create a taxable footprint that nobody intended, and the thresholds vary from treaty to treaty rather than following a single universal figure. We surface these before they become an enquiry.
How We Run the Corporate Return
We start with a residence and presence review so the filing position is settled before any numbers are drafted. From there we map the group, identify every cross-border flow, and decide where relief is due and where a charge arises.
We prepare the corporation tax computation and the CT600, coordinate with your overseas advisers where a foreign return has to agree with the UK one, and keep the treaty and residence analysis on file so the position is defensible if HMRC asks. The work repeats each period, which is the point of an engagement rather than a one-off note.
What the Corporate Tax Work Costs
We work to a fixed fee agreed before we start, set against the shape of the group and the number of cross-border flows involved, so you are not exposed to an open-ended hourly bill on a recurring compliance job.
If the engagement widens into transfer pricing documentation or a structuring review, we scope and price that separately rather than folding it into the corporate return. You can start from the international tax accountants homepage to see how the services fit together.