My landlord has 'opted to tax' our studio building — what does that mean for my rent?

Your landlord isn't doing anything underhand — opting to tax is a standard mechanism. Supplies of land and buildings are normally exempt from VAT, but an owner can choose to 'opt to tax', which makes rental income subject to VAT at the standard rate, currently 20%. That's why 20% has appeared on your rent invoice. Why would a landlord choose this? Once they opt to tax, they can reclaim the VAT they incur on costs relating to the building — refurbishment, maintenance, agents' fees — which they couldn't recover if the rent stayed exempt. So it's almost always driven by their own input VAT position, not by anything to do with you. For you as tenant, the rent is effectively 20% higher in cash-flow terms. But the key point: if you are VAT registered and your own supplies are taxable, you can reclaim that VAT as input tax on your return, so it costs you nothing overall. Since you're not VAT registered yet, you can't reclaim it — for now it's a genuine extra cost. If you're about to cross the registration threshold, registering will turn this from a cost into something recoverable, which strengthens the case for registering promptly. Practically: ask your landlord for confirmation of when the option took effect, and check whether your lease allows VAT to be added on top — some older leases are written as VAT-inclusive.