Do I need to tell Companies House when shareholdings change in my company?

You don't file the transfer itself with Companies House — but you do need to make sure the change is reflected on the public record.

First, the internal step: record the transfer in your company's statutory register of members and keep the stock transfer form. You've already done this, which is exactly right — that's the legal record of ownership.

Second, the shareholder information at Companies House: shareholding changes are reported through your confirmation statement (filed at least every 12 months), not as a separate filing. The new 70/30 split will appear there.

Third, the PSC position — this is the one with a real deadline. A PSC is anyone with more than 25% of the shares or voting rights. Your partner at 30% is now a PSC, and you must tell Companies House about changes to PSC information within 14 days of the change. This is a separate filing from the confirmation statement, and failing to do it is an offence, so if the transfer was earlier this year and you haven't done this yet, file it now.

Finally, your partner as a new PSC will also need to verify their identity for Companies House and provide their personal code.

In short: internal register updated now, PSC notification within 14 days, shareholder details updated on the next confirmation statement.