Retired Army Staff Sgt. Daniel F. Purinton, 71, has argued for almost two years that the Department of Veterans Affairs owes him an additional $8,044.

Purinton said the underpayment occurred as Department of Defense and VA officials implemented a complex series of laws, starting in 2003, to end for many retirees the ban on "concurrent receipt" of both military retirement and VA disability compensation.

Purinton is right, but he also is far from alone. Back pay is owed to roughly 20,000 recipients of Combat-Related Special Compensation and 78,000 recipients of Concurrent Retirement and Disability Pay. Total back pay owed is said to be in the hundreds of millions of dollars.

Within the next two weeks, defense officials hope to resolve final details with the VA on how their underpayments will be calculated, how processing costs will be shared between departments, how retirees will be notified, and when most of these retirees can expect to be paid.

Most of the payments have to be calculated manually, rather than by computer, so it could take six months for retirees to be fully compensated, officials explained in a draft press release shared with Purinton.

Those eligible for back pay have combat-related injuries and illnesses or service-connected disabilities that the VA rates as at least 50 percent disabling. All of them also had military careers of 20 years or longer.

The delay in fully compensating these retirees can be blamed in part on the twisted path Congress chose for bringing some disabled military retirees relief from the century-old ban on concurrent receipt.

The ban requires that retirees who receive tax-free VA disability compensation accept a matching reduction in taxable retired pay. The dollar-for-dollar offset remains in effect today for retirees with noncombat disabilities of 40 percent or less. Also left out of recent law changes are veterans forced by their disabilities to retire short of 20-year careers.

A total of 222,000 military retirees, however, have seen their incomes climb as a result of CRSC, CRDP or both. Almost half of them, whether they know it or not, are owed more — in some cases thousands of dollars.

CRSC took effect June 1, 2003. Early payments were limited to active-duty retirees who applied and were found to have combat-related disabilities of at least 60 percent, or disabilities of at least 10 percent for which they received the Purple Heart. Eligibility was expanded on Jan. 1, 2004, to retirees having any combat-related disability including reserve retirees.

CRDP, which took effect Jan. 1, 2004, is payable to 20-year retirees with disabilities rated at least 50 percent but not tied to combat. CRDP payments are being phased in and will end the retired pay offset for seriously disabled retirees by 2014. The size of the reduction varies by level of disability. Changes for 2005 and 2006 will end the retired pay offset faster for the most seriously disabled retirees.

Dealing with the complexity of CRSC, CRDP, military retirement and VA compensation has stressed the VA and the Defense Finance and Accounting Service and frustrated some retirees.