Sold/bought meme stocks for years. Finally made a total profit. How to work out & pay tax?

isushi

In hindsight, I am ashamed to admit this, but... 

I got into GME meme stock a few years ago. It went down in price and I panicked sold for a loss and then re-bought more for a few years and "averaged down". This made my average per share stupidly high. 

This was in Revolut as I had no idea about tax implications. Eventually, over 3 years I sold for an overall loss bit by bit and decided to re-buy in a Stocks ISA for a lower price which helped me average down a little more.

Luckily, GME stock shot back up again this financial year. I sold it in my Stocks ISA for a profit overall.

However, I still had shares in Revolut that I sold and made a further £30k profit on. 

The problem is that given that I did the above in a stupidly panicked and unorganised way... I will need to spend a while working out the tax I need to pay (or get a professional).

Any idea how I work out the tax when I have been buying/selling for a loss over years? Do I get to claim anything for tax due to selling for a loss for the previous 4 years? Is the £30k profit in Revolut taxed based on the average cost in Revolut after selling & rebuying in the Stocks ISA or from the beginning when I bought stocks. 

When I started I wasn't in the 40% tax bracket for work, but this financial year I am after a wage increase at work. 

Grateful for any advice given how stupid / lucky I was. I know I don't need to submit it until next year, but planning on buying a house, etc. and don't want to suddenly find that I don't have enough to pay tax. Although I might have messed up already by not submitting losses for previous years. 

I'll be honest, the loss in the beginning hit me hard and I was depressed/anxious/panicked which meant a lot of denial. I've learned my lesson and now out of stocks for until I am in a position to do it in a responsible way and have my life sorted. 

eskbanker

Firstly you need to ignore anything to do with ISAs when calculating CGT liabilities, so any gains made within that wrapper have no tax liability, which is the whole point of using ISAs!

So, you need to work out the base cost of the holding that stayed outside the ISA and calculate your chargeable gain from that.

Hoenir

You need to dig out the contract notes for the purchases and sales. Then calculate your gains and losses systematically. Losses need to be reported within 4 years after the end of the tax year in which the disposal took place. In order to be carried forward and offset against profits made. 

Easy enough to calculate using a spreadsheet.