Only because it is a rush
"Titular" has a dozen possible translations; it all depends on the "sociedad" it refers to here. Generally speaking, owner can work, but not for a sociedad civil... You could use title-holder or even legal representative. For titularidad, though I would need to be more familiar with the particular circumstance to give you a definite definition, "holdership" is my first instinct.
Best of luck
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