This IRS Letter 2644c indicates that they are delaying action on your case because they lack information to process it. Sometimes, you will wait on the IRS to act & other times, they will ask for & expect a response from you. (See also, Notice CP2006)
Respond to Letter 2644C
If they request information from you, just give them the information they desire so the account can continue. It may require some effort, though. The IRS will expect a fully prepared response, not a pile of documents sent to them.
But, even so, the ultimate resolution depends upon the action of the IRS, which you must ensure is occurring by keeping track of what the IRS is doing & initiating correct procedures when & where appropriate. When the IRS is not acting, nothing gets done. So you must make them act. You must follow up - don't depend on the IRS. Follow the Prep Steps to win!
It would be wise to follow the IRS advice & continue to make payments, if you are obligated. You don't want to default on the agreement with the government.
To get a case review, please follow the Prep Steps & contact Tax attorney J. David Hopkins at TaxHelpLaw for quick answers & an Action Plan for a head-start advantage!