I'm afraid that you cannot claim income tax relief for your loss. As you will read here, all you can do with it is to claim relief against capital gains in the two years prior to your claim so long as it was irrecoverable then, the year of your claim or in in future tax years.
I hope this clarifies your position but let me know if you have any further questions.
I think you are asking if you can claim tax relief for the value of the time you spent maintaining the property which you received no payment for. I'm afraid that the answer is you cannot.
You might try claiming bad debt relief but unless you invoiced for the work, you may struggle to get it past HMRC. It's worth a try but you need to be clar in your tax return what the bad debt claim relates to as HMRC will almost certainly ask about it.
I have to go out for about 30 minutes but will be back.
As you invoiced for the maintenance feesand I assume accounted for those invoices in earlier accounts, you should claim bad debt relief in your latest self-employed accounts. Box 27 on page SEF2 of the full self-employment pages is the box you use for bad debts.
You should claim the capital loss in your tax return capital gains pages to establish it with HMRC.
Would you mind rating my asnwer before you leaver the site please.