The income from residential letting properties is not treated as trade income, as there is insufficient activity to constitute trade income. The ownership of residential letting properties is deemed to be a form of investment and therefore you do not need to register a partnership business with HM Revenue & Customs. Likewise, because it is a form of investment, National Insurance Contributions are not due on this source of income.
Where a husband and wife have joint investments, the income arising is assessed equally on a 50:50 basis, unless the property is actually owned in different proportions AND a joint declaration is made to that effect. Assuming that you hold the property equally, you would each need to declare 50% of the income received and expenses incurred to the Revenue.
If you do not currently have income that fully utilises your personal allowance, you could consider having the properties held in your sole name so that all rental profits are assessed as your income. Under the current capital gains tax legislation, there are no implications for transfers between a husband and wife, but there would be some legal fees incurred.
The long term capital gains tax and inheritance tax position should also be considered, especially if the properties are owned outright. You should seek professional guidance from your local TaxAssist Accountants office before making any decisions that may have a bearing on any of these taxes.