In my buy-to-let property, I have ten windows and a patio door - some are in urgent need of replacement, some moderate need of replacement - and the others are okay-ish, but could do with being upgraded to modern double glazed standard. I want to get them all replaced at the same time – it just makes it easier all round - except perhaps when it comes to determining whether this is a repair or capital expenditure. I know that HMRC are (now) much relaxed about single glazed windows being replaced with double glazing, but does every single window need to be in a state requiring replacement in order to qualify as a repair expenditure. I am wondering if I: (a) can treat them all as a repair? (b) must treat them all as capital? and (c) can apportion between repair/capital appropriately - the ones that need replacing are the most expensive ones?

Given that HMRC accept (see: www.hmrc.gov.uk/manuals/pimmanual/PIM2020.htm) that replacing single glazed windows with double glazing is not considered an improvement, i.e. a capital expense, from what you have described I would say that all your expenditure is revenue. Even those windows that are okay-ish should qualify for this treatment, because a taxpayer is entitled to replace a 'worn-out' fitting with something new that is more presentable, and claim it as a revenue expense, if the replacement is essentially 'like for like'.