When are courts "JURISDICTION-LESS" re: counterclaims?

It is settled that any decision rendered without jurisdiction is a total nullity and may be struck down at any time, even on appeal before this Court.

In the present case, considering that the trial court did not acquire jurisdiction over the permissive counterclaim of Rosita, any proceeding taken up by the trial court and any ruling or judgment rendered in relation to such counterclaim is considered null and void. In effect, Rosita may file a separate action against Arturo for recovery of a sum of money. However, Rosita's claims for damages and attorney's fees are compulsory as they necessarily arise as a result of the filing by respondents of their complaint. Being compulsory in nature, payment of docket fees is not required. Nonetheless, since petitioners are found to be liable to return to respondents the amount of P3,000,000.00 as well as to pay moral and exemplary damages and attorney's fees, it necessarily follows that Rosita's counterclaim for damages and attorney's fees should be dismissed as correctly done by the RTC and affirmed by the CA. (G.R. No. 155033; December 19, 2007)