In 2011 I sold a property in Bulgaria and made a capital loss of £33,000. Being very naive of tax affairs I did not report the loss to HMRC. In 2017 I sold my Buy to let property in the UK. This prompted me to complete my first ever self assessment tax and submitted to HMRC. As a consequence of this I also realised I would have to make a disclosure (under the let property campaign) for the buy to let rental business. After a lot of research, HMRC have accepted that I made a loss on the UK Buy to let property each year and have agreed with my workings. However, whilst researching the disclosure and building evidence I realised that I could have set the capital loss made with the sale of the bulgarian property against the capital gain in 2017. However, due to ignorance I did not notify HMRC of the loss within 4 years from 2011. HMRC have refused to carry forward the loss. Are there any possible reasons how I might appeal this e.g. Under the terms of the let property campaign or by pleading ignorance?