Trainline, the online rail ticket seller, has kept its full-year guidance unchanged, but flagged the Competition and Markets Authority (CMA) investigation into its booking fees as a heightened risk.
It expects net ticket sales, the total value of tickets sold through its platform, of £6.2 billion to £6.45 billion for the year to February 2027.
Underlying revenue is forecast at £440 million to £455 million, with adjusted earnings before interest, tax, depreciation and amortisation (EBITDA) at about 2.9% of net ticket sales.
The underlying revenue figure excludes any one-off adjustments that might arise from the CMA case.
The competition watchdog opened its investigation in August into how Trainline presents mandatory booking fees during the booking process.
Trainline has set aside a £3.7 million provision, including legal fees, and booked a £4 million exceptional charge.
It stressed this is not an admission of wrongdoing, and said the outcome could differ materially in either direction.
The CMA is due to give its next update in January 2027.
The regime being used only came into force in April 2025, leaving little precedent to judge possible fines or redress.
Revenue for the six months to 31 August slipped 1% to £233 million, as tighter industry refund rules cut the number of refunds and the fees Trainline earns on them.
Net ticket sales were flat at £3.26 billion.
Adjusted EBITDA rose 7% to £100 million, helped by a 36% cut in marketing spend.
Operating profit fell 5% to £64 million on higher depreciation and the CMA charge.
The International Consumer arm turned profitable for the first time, with adjusted EBITDA of £6 million against a loss of £8 million a year earlier.
In the UK, revenue fell 5%, hit by fare reform, a regulated fare freeze and train operators steering customers to their own websites.
Ancillary revenue, from add-ons such as insurance, grew 22%.
Chief executive Ian Brown said the industry regulator's draft code for how retailers deal with Great British Railways, the new state-owned rail body, "needs further strengthening".
Net debt rose to £212 million, or 1.2 times EBITDA, after £86 million of share buybacks.
A new £100 million buyback started in September, taking total repurchases since 2023 to £356 million.
