Posthumous freeing of slaves

[Hanny]

I came across something curious over the weekend:

Scissa was giving a very elegant novendial in memory of her poor old slave, whom she had enfranchised after his death. And I suppose she will have a good round sum to pay to the tax-collectors, for they do tell me the dead man's fortune came to fifty thousand.

Petronius, The Satyricon, 10., emphasis mine

Was there posthumous freeing of slaves? If so, why?

I suppose that this could be a way of honouring the deceased, as is hinted in the text, but I can't really think of any other reason to do so. If the posthumously-freed man had children, would they become free citizens?

I also guess that the ex-slave’s assets are still counted as owned by the lady Scissa, since Trimalcho says she will have to pay the taxes.

The 2% to 5% tax is the emancipation tax (Vicesima libertatis) the owner pays to the state.

 I think your right, to be a citizen you had to be born free,so freeing a person after there death would make the slaves wife ofspring free at birth rather than a slave at birth and avoid macula servitutis.