Credit memo for Tax does not create distribution lines

We have charged sales tax to our customer and want to credit it back. Her is what we did:- Opened the original transaction - action menu credit. entered the tax as 100% it picked up the tax amount from the original invoice and we hit credit lines. (After entering the transaction type etc) The credit memo is generated however, there are no distribution lines for the Tax. Can some one point to where the issue could have been?

There are 3 transactions like this. All help appreciated.

Thanks,