Claimants usually receive their award letters within a few months of Social Security approving their disability applications. However, Social Security does not have a set deadline for issuing award letters. Some claimants will get their letters very early, and some claimants will still be waiting for their award letters even after Social Security has issued the first disability payment. In general, Social Security issues award letters faster for claims that are approved without a hearing. If your case has gone to an ALJ hearing, then you may wait longer for your award letter.
Why don't you get your award letter right after your claim has been approved? After your claim is approved, your file is sent back to a field office so that Social Security can check on your continued eligibility for benefits. For SSDI, that means that a representative will be looking to make sure that your established onset date is before your date last insured and that you have the work credits you need to qualify for SSDI. For SSI claimants, the field office will be checking your income and resources to make sure you are eligible for SSI.