While I believe this is better answered by someone with SSD expertise, if the government is asking for it, you probably have no option but to provide the requested information. I do know that there is some interaction between the two and the LTD carrier may be entitled to reimbursement subject to the length of time and amount of benefits you've been receiving LTD. You should consider consulting with an attorney that specializes in SSD matters.
Disclaimer- The information you obtain at our web-site or through postings on such sites as this is not, nor is it intended to be, legal advice. You should consult an attorney for specific advice regarding your individual situation. Any response given here is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response may change appropriately.
Whether they are entitled to that information depends on the terms of the policy. Definitely get a copy of it and have an attorney who specializes in LTD claims look at it for you.
An insurance policy is like any other contract. Whether you are required to provide the LTD insurer with a copy of the SSD appplication and determination will be set forth in the policy. Some LTD policies call for the LTD benefits to be offset by any SSDI benefits, and such policies would, most likely, require you to provide copies of everything submitted to SSD. It all depends upon the wording of the policy. You should have a lawyer who is familiar with insurance read the policy for you and advise you as to whether the insurer is entitled to this information.