As the official word _solventa_ means "pagokapabla", capable of paying, and of course qualifies a natural or legal person, I would propose for the liquid capital ***solventiga***, because according to my (layman) understanding liquid capital is such capital which makes the owner solvent.

Another possibility would be *neligita* (in the meaning 2 of ligi according to PIV: "limigi ies liberan agadon") or *neblokumita*.