Historic tax allowance claim attempt - any advice?
I've been self employed for ten years, and my home address is my business premises. I run a fully licensed dog daycare full time from home.
Since moving over to making tax digital (sooo much easier) I've realised that I am actually entitled to working from home allowance as I WFH more than 103 hours a week (it's actually 160) - apparently this means that I'm entitled to £312 tax allowance per year. Have no idea how I missed this and I'm really annoyed at myself!
How far back can I amend my self assessments? And what do I need to include to mail to HMRC? Do I need to include paper amendments for every single year? Seems like such a faff, but I would like to get the refund for as far back as I can get
Many thanks