Hello and welcome to the site. Thank you for your question.
Your understanding is correct –
If you live together with your spouse or civil partner, HMRC normally treat income from property held in your joint names as if it belonged to you in equal shares and tax each of you on half of the income, regardless of actual ownership.
If you wish the share to be on actual ownership basis, then you need to complete Form 17.
Please complete this form if you want to be taxed on your actual shares (known as `actual basis'). You will also need to provide evidence that your beneficial interests in the property are unequal, for example a declaration or deed.
The benefit is that the person liable for IT on rental income is also liable to CGT at rates appilcable to that person only.
The disadvantage is that you get one gains allowance instead of two.
More information on this can be found here. The link will also help you with completion of form.
I hope this is helpful and answers your question.
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