Firstly you assign a proportion of the actual property (yes I know youre wishing to calculate a value against the rental income) called a beneficial interest in the property. So in reality youre looking at say transferring a 25% beneficial interest in the property.

What you need to be aware of is it can be difficult revoking a DoA if one party doesnt agree. Whilst yes technically you remain the documented sole owner, your spouse in reality is entitled to 25% beneficial interest in the value of the whole property, not simply any rental income. If you divorce, she automatically has a 25% claim on the property, same if you died, or she died. Her beneficial interest remains and is part of her estate. You cannot unilaterally revoke a DoA.

Secondly, you will both then need to calculate costs relating to the rental income in the same split. So have you done the maths? Your spouse cannot assign 100% of the tax allowable costs against her 25% share of the income.

Thirdly, You may also need your mortgage lenders permission if you have a mortgage on here as in effect, youre giving away 25% of the house.

All these things need to be considered, but ultimately in answer to your question regards a calculation of ‘equivalent value against the rental income’, it must be gross, as you cant assign 100% of the costs to your 75% share either. Both tax returns must reflect the 75/25 split on both income and expenses from this property.

HMRC have also confirmed that while you can assign the beneficial interest to someone else, you can’t assign the mortgage costs to them as the mortgage is in your name.