I dabbled in a few dodgy altcoins, which have effectively gone to zero.
I can’t sell them as nobody will buy them, how do I realize the loss?
Thanks
Hey there @Brian_Callinan 
In such cases, you could send them to a burn address, and this will show in Koinly as a disposal for 0, and you would realise a loss.
The other way to potentially handle this is to tag as Lost and then speak with an accountant or tax professional to understand if you can offset this.
If you are based in the UK you can make a negligible value claim. If you google it most of the info you find is related to shares but the exact same rules apply to crypto. It involves writing a letter or submitting it with your self assessment tax return to HMRC with the details. More details below for UK users.
The difficult bit is tricking Koinly to do the calculation correctly as they don’t have a feature that implements this correctly as tagging the coins as lost doesn’t following the HMRC procedure.
How I achieved this in Koinly, say for example you own 1000 “ABC” tokens. You create a manual transaction for selling 1000 “ABC” token’s for £0.00. This will realises the loss in koinly. However as per the HMRC guidance you are suppose to still show that you own the tokens but with zero cost basis(makes sense as you still do own them as you haven’t actually sold them). To achieve this you then create a second manual transaction that is 31 days after the first one where you buy 1000 “ABC” tokens for £0. It is really important that the second manual transaction is 31 days or more later so Koinly doesn’t apply the 30day BNB rule.
This means Koinly will have realised the loss but the full CGT report shows you still own 1000 “ABC” tokens. That’s quite important as HMRC will probably want to see the full report for the year you make the negligible value claim to accept it.