I find this all very stressful. I've now downloaded BitcoinCore and the blockchain, and created a raw transaction that looks something like this:

{
  "txid": "FirstLongNumber",
  "hash": "FirstLongNumberagain",
  "version": 2,
  "size": 158,
  "vsize": 158,
  "locktime": 509839,
  "vin": [
    {
      "txid": "PublicKeyForMyMinedBitcoins",
      "vout": 0,
      "scriptSig": {
        "asm": "SecondLongNumber[ALL]",
        "hex": "ThirdLongNumber"
      },
      "sequence": 4294967294
    }
  ],
  "vout": [
    {
      "value": 49.99943486,
      "n": 0,
      "scriptPubKey": {
        "asm": "OP_DUP OP_HASH160 FourthLongNumber OP_EQUALVERIFY OP_CHECKSIG",
        "hex": "FifthLongNumber",
        "reqSigs": 1,
        "type": "pubkeyhash",
        "addresses": [
          "MyLedgerAddress"
        ]
      }
    }
  ]
}

I've redacted all the long numbers just in case there's anything sensitive there. The big 'gotcha' it seems is that if you're not careful and don't either spend the lot in one transaction or create a second output going back to yourself, then any change will go to the miners. The intuitively sensible thing to do is to send one bitcoin just to test and see whether it works, with the intention of sending the rest later. This would be a very bad idea as you would be donating a mining fee of 49 bitcoins!

So there ends the limits of my understanding of raw transactions. I'd be very grateful if anybody knowledgeable could look over the redacted transaction and tell me whether there's anything else I might have gotten wrong?

Hmm... In what way can you get a speculative income from Bitcoin? The methods I can think of are 1) having mined a block before mining became a commercial proposition and 2) having bought in very early on when it was an asset class unlike any other, and therefore by definition speculative. 3) having gambled using bitcoins. Perhaps it's this latter possibility to which they are referring.

Somehow 20% tax feels a lot less punitive than 28%. I think I'll contact HMRC directly and see whether they can clarify what they meant by their phrase about speculative income.

Thank you for that! I had somehow missed that the 28% rate applied only to gains on residential property and carried interest. I think I must have been reading some older pages on CGT as I get the impression the rules have changed. Anyhow, it means I have considerably more money to spare than I thought.

I think your other advice is good, but not applicable to me. Basically I sat on my £10 worth of bitcoins for 7 years until they came to represent a life-changing amount. About £300k all told. Paying off the house is a big deal - I'd be really upset if I lost out on it. If BTC goes to $0 tomorrow it's been a fun adventure and I've done well out of it and won't be sad. I've hung on to a few as I think it more likely that they'll go up, but there's no guarantee of that. So the coins are now cash, but I had to convert a sufficient sum within this tax year or else I would have risked missing the boat. I wouldn't have cashed out at all last year as they would have represented a nice but not life-changing amount of money.

There's no question that I will be speaking to an accountant. My question is whether I should be talking to a specialist accountant, e.g.:

https://www.dnsassociates.co.uk/blog/bitcoins-tax-implications-uk

or whether the accountant up the road would be likely to do an equally good job.

I suppose the other option would be talking to HMRC directly as it appears I may not have to pay tax at all:

https://bitlegal.io/2015/05/05/tax-treatment-of-speculative-digital-currency-transactions-uk/.

I feel slightly ambivalent about this as I am quick to condemn tax-dodging companies or rich people who use loopholes. I work in the public sector. Taxes pay my wages, and I work very hard for them. On the other hand, I wouldn't condemn anyone who won the lottery and didn't pay tax... and I feel as if I've won the lottery. One day my overdraft and credit card hit -8K so I dusted down my old computers and found I'd bought 10 x more bitcoin than I remembered. Had I known how well they were going to do, I'd have spent £20 rather than £10.

So... I've cashed out enough Bitcoin to pay off the mortgage and pay 28% capital gains tax on it. I spent £10 on Bitcoin in January 2011 when you could still buy them with Paypal.

I've outlined the situation briefly to my Mum's accountant who says it all sounds pretty straightforward. Obviously I visit exchanges and read Bitcoin news and google therefore sends me lots of adverts for accountants who specialise in dealing with Bitcoin tax issues.

Is there any point in going to one of these firms? It strikes me that I might end up paying them a lot of money for advice on a straightforward issue. I know there is a suggestion that sufficiently speculative transactions count as gambling and are therefore untaxed. However whilst it feels as if I've won the lottery, another part of me feels that it was just a particularly good investment and should have been treated as such. In which case, simple..?

Thanks for the suggestions. I'm afraid my private key isn't going anywhere near the internet though, btcspot.

I'm going to try the bitcoin-core method - had just hoped there might be something simpler. It's a lot of money to lose if I screw up! I'm also going to need a clean computer. Anything with the key on it isn't going back on the intermet!

Hi all. I downloaded bitcoin 0.3.2 a while ago, and as I only ran it on an anaemic EEPC, I only generated 50 bitcoins. That doesn't mean to say I wouldn't like to get control of them again.

My public address is:

18jRv4R1i1MSXNYfmCL1dYvSaXaZBb7Cb1. The blockchain explorer seems to show that the funds exist i.e. there are 50 bitcoins there + a fraction of a coin I sent on the 'hit it to make it work' principle.

However when I imported my private key to Electrum it initially showed 50 coins present but couldn't make a transaction to sweep the coins to my new wallet and it gave me an error message "16: mandatory-script-verify-flag-failed (Non-canonical DER signature)". Now for some reason Electrum only shows 1 microbitcoin, but blockchain info shows 50.001 bitcoins and so does my wallet with Mycelium. However, when I try to make a payment with Mycelium or sweep the coins to my TREZOR, it shows that I have 0.00 bitcoins.

I just made one test payment from the address (a fraction of a microbitcoin) which seemed to work, but aside from this blockchain.info shows no record of transactions from this address.

Have I had my bitcoins stolen? Were they never there in the first place? Is this just some bug which can be fixed somehow? I'd be glad of any explanations/pointers as to what to do next.