The IRS published T.D. 9727, the final regulations under IRC Sec. 6402. The final regulations state that unless otherwise directed by the IRS, a claim for refund or credit should be filed with the IRS service center where the taxpayer CURRENTLY would be required to file a tax return for the type of tax to which the claim relates, irrespective of where the tax was paid or was required to have been paid. Other than some minor changes, the final rule mimics the proposed regs issued in 2011. The T.D. includes all the procedural aspects of filing a claim.
The old general rule required that the claim be filed with the service center for the IRS district where the tax was paid.