From a recent report by Social Security's Office of Inspector General (OIG):
For the 250 randomly sampled Title XVI claims involving claimant representative fees, SSA withheld fee s from claimants’ past-due benefits and paid the fees directly to the claimant representative. However, our review found that SSA did not always pay the appropriate amount when it paid the claimant representative fee on concurrent Title II and XVI claims. As a result, when SSA overpaid the claimant representative, it generally underpaid the claimant. Similarly, when SSA underpaid the claimant representative, it generally overpaid the claimant.
Of the 250 sample claimant representative fees, 10 (4 percent) had claimant fee payment errors totaling $13,020: $12,479 in overpayments and $541 in underpayments. The payments ranged from a $3,062 overpayment to a $484 underpayment. Based on our results, we estimate that 15,200 claimant representative fee payments had about $19.8 million in payment errors for Calendar Years 2011 and 2012.
We acknowledge that computing past-due benefits and the related claimant representative fees may be complex, as staff is required to analyze a multitude of factors and make various decisions to pay the past-due benefits and fee. ...