What is Section 24 and how does it affect landlords?

It is the rule that stopped individual landlords deducting mortgage interest as an expense. Instead you get a tax credit worth 20% of the interest.

For a basic rate taxpayer the outcome is broadly similar to the old system. For a higher rate taxpayer it is not, because the rental income is counted in full before the credit is applied, which can push you into a higher band on paper.

It applies to individuals, not to companies, which is the main reason limited company buy to let became common. Whether that route makes sense for you depends on your income, your plans and your existing portfolio.