At any turnover. There's no threshold, no phase-in date, nothing to prepare for on the company side.
MTD for Income Tax only ever touches Income Tax — and a limited company pays Corporation Tax, not Income Tax. The two systems are separate.
More than that: HMRC confirmed in its Transformation Roadmap (21 July 2025) that it is not proceeding with "MTD for Corporation Tax" at all. There's no date, no pilot, no current plan.
Corporation Tax basics on GOV.UK →If either of those applies to you, the sole trader or landlord guide covers what's actually relevant to your situation.
Sole trader guide → | Landlord guide →Your Corporation Tax filing carries on as before — annual accounts to Companies House, and a CT600 return to HMRC.