This is a regular verb. It follows the conjugation pattern of the verb falar.
This verb is more common in Brazilian Portuguese. In European Portuguese, pagar or saldar are more commonly used depending on the context.
Present:
A Ana quita a dívida.
Ana pays off the debt.
Preterite:
O Miguel quitou o empréstimo.
Miguel paid off the loan.
Conditional:
A Clara quitaria tudo.
Clara would pay off everything.