There is no way to tell how long it will take for a creditor to respond to a settlement offer. If you have sent the offer by Certified Mail with a Return Receipt like UGotiate has suggested, this will allow you to know when the creditor has signed for and picked up your letter at the post office.
Each creditor will handle each account and each offer differently. Some creditors will respond to offers right away while others will take longer. And there will be some creditors that never respond. This is just part of the negotiation process and it does take patience. If the creditor does respond, it will likely be in the form of a mailed letter. The creditor may accept the offer, reject the offer or suggest a counter offer for settlement.
The good news is UGotiate helps you keep track of your offers and responses. UGotiate prompts you to indicate if you’ve received a response from a creditor and will guide you on what to do next depending on if you’ve heard back from the creditor or not.