There are sufficient circumstances to permit a tax write-off of your SLI investment. 

Should the company be revived then you will have to reverse the write-off.

Ask your tax preparer or tax accountant if you should, and any questions you might have about doing so. 

And taking the write-off does not strip you of your ownership of your shares. You will still be holding the bag. 

And do not believe me, (even though I am absolutely correct) ask your tax expert.