Tax Query for Remittances - HMRC Penalty?

I have received my ILR in mid 2018 via Tier 1 General Route. I am planning to apply for my citizenship application next year.

I have never been self-employed during my stay in UK. Last year, I worked only till Aug 2018 and has not been working since then. I had some savings in NRE Savings account in India which was remitted from my UK salary. As I was not working for the past one year, I had transferred this money almost back to UK during various 3-4 times totaling to £15,000.

Last week I received my P800 for the tax year 2018-19 saying HMRC owes me some money as I have not utilized my Personal Allowance via PAYE as I worked only till August 2018.

My query is should I be filing a Tax Self Assessment form for the money that I have remitted for living expenses? Would I incur any HMRC penalty if I don't file?

I would be quite grateful if somebody can help me point to any previous instances of such a similar case in this forum.

This is 100% tax question, nothing to do with immigration.

For purposes of taxation, it doesn't matter when you got your ILR or any other type of residence. Even a citizenship wouldn't change anything.

A few years ago, I wanted to open a business with my brother. I sent him £10'000 saving I had. This money was already taxed as I saved it from my salary. We never opened that business and we decided to cancel everything. He then sent me my money back. I didn't fill anything and I don't think I had to. I kept all the proofs required to justify the movements of the money.

But see with a tax adviser or ask in a forum specialized in tax maters.

Thanks Zerubbabel for your reply.

I'll take some professional advice regarding this matter.