There is no specific percentage that guarantees a successful debt settlement. After all, creditors have no obligation to liquidate or forgive any part of your balance. That said, most successful liquidations usually result in paying 30 to 50% less than the original balance. Some debt collectors want between 75 and 80% of what you owe. Others will keep 50%, while others might settle for a third or less.
So, it makes sense to start with your first offer and see what happens. The original creditor can obtain tax savings of approximately one-third of the amount of any uncollected debt. Therefore, they are more likely to reach an agreement if you offer them more than they can get in tax savings. Before suggesting a lump sum, determine the maximum amount you can afford and don't give in.
Start with a low supply, such as 25% of the debt you owe, and try to reach a midpoint. Your debt collector may accept a lump sum of between 25% and 50% of the total debt, but that's no guarantee. Some collection agencies require the full amount of debt, while others are willing to work with debtors to varying degrees.