When recording these transactions, my main aim is to preserve the capital value I am holding.
First, the special dividend should be recorded as a dividend, hopefully franked.
Then, the cash return is a return of capital so will reduce the capital value of Tatts shares you held.
You now have the reduced/residual capital value of your Tatts shares.
If you don't have TABCORP shares, you could simply do a restructure to 0.8 new shares per old share and rename the security, ie a non-capital gains event.
Or you could document sale and buy transactions for the same capital value. Two possible capital values could be used.
1) I would document sell/buy for the residual capital value of Tatts shares, documenting that no capital gains event took place.
2) Alternatively you could document sell/buy for the current market value of Tatts shares. This may be a capital gains event.
The documentation supplied by Tatts will probably indicate if this is required, ie a capital gains event needs to be declared.