Companies House doesn't recognise "alternate director" as a separate officer type, so Inform Direct has no dedicated appointment process for it. If your company's articles permit alternate directors, you appoint one the same way as any other director — see How Do I Appoint an Individual as a Director? — and Companies House registers them as a director in the usual way.

The "alternate" designation itself is an internal, constitutional matter governed by your articles, recorded via board minutes rather than a separate Companies House filing. Inform Direct's template library includes board minute templates for appointing and removing alternate directors, plus a letter notifying the company of an alternate director's appointment — use these alongside the standard director appointment to document it properly.

Whether your articles actually permit alternate directors, and on what terms, depends on your specific articles — check these, or speak to a solicitor if you're unsure.