Record who owns what, so the tax figures are yours and not the property's.
Tell Abodient who owns a property, and what share each owner has, so your tax is worked out on your portion.
Open the property and choose its Finance tab. The button beside Rent status says how the property is held: Held personally, your company's name, or Managed for and an owner's name. A shared property adds · shared. Select the button.
A menu called How this property is held opens. It lists who owns the property and each share, then your UTR. If a company owns it, the menu shows the company number instead.

Select Change who owns it. A window called Who owns this property? opens. It is the same window wherever you start from, and the last section lists the other places.
The window has three choices across the top:
Nothing changes until you select Save. Cancel closes the window and leaves everything as it was.
With Me chosen, select + Someone else owns part of it. An Owners list opens. You are the first row.

The Taxed line under the total says where each share is taxed. In the picture, 60% goes on your Self Assessment and 40% on the spouse's own return. Select Back to one owner to go back to owning it alone.
A company you own can hold part of a property with you. Open the window on a property you own personally, select + Someone else owns part of it, then open the drop-down in the second row. Your companies are listed there. Pick one. A company row needs no name typed, because it uses the company's own, and the Taxed line then names the company's Corporation Tax. + Add a company… adds one that is not on the list yet.

If a save moves a share between you and a company, we ask you to confirm first. The question reads Move and a percentage, for example Move 50% of this property to the company's name. In law that is a disposal, so stamp duty and Capital Gains Tax may apply. We record the split. We do not transfer anything. Speak to your accountant first.
If you hold a property with a spouse or civil partner, HMRC treats the income as 50/50 by default, whatever the deeds say. The window reminds you of this when you pick Spouse or civil partner.
That changes only if you have filed a Form 17 election. If you have, set the real split. If not, leave it at 50/50. The rule applies only between spouses or civil partners. It never applies when a company owns part.
On One of my companies, the same + Someone else owns part of it link opens the owners list with the company at the top. You cannot be on that list. If you own a share yourself, the property counts as held personally, so enter a split between you and a company from Me.
Your books stay whole. Rent, costs and cashflow keep showing everything the property earned. Only your tax figures use your share.
Changing the answer can remove what was set before. If the property had owners and shares, the window says Saving removes the owners and shares and lists them. Choosing For someone else does the same, because a managed property has no owners list.