I assume a letting agent will deduct and pass on the basic tax rate to HMRC on a quarterly fashion and at the end of the year they will provide a document explaining how much tax you have paid.
When I come to do my tax returns, I can state the tax which was paid and any further deductions such as necessary tests and any key maintenance prior to or during the tenancy to make the home acceptable for habitation within a tax year (April to April)
I assume I must evidence the bills or will you ask if you need further clarifications?
What makes you assume that? I’m not aware that this is a regular letting agent function and indeed would be something that would need to be paid for separately IF it was available.
Its only a legal requirement if the landlord doesn’t make an arrangement with HMRC directly or the tenant deduct the tax at source, which means that most agents won’t have any/much experience of doing it and it would likely be an extra you’d have to request and pay for.