Although we believe that our tax estimates are reasonable and that our tax filings are prepared in accordance with all applicable tax laws, the final determination with respect to any tax audit or any related litigation could be materially different from our estimates or from our historical income tax provisions and accruals. The results of an audit or litigation could have a material effect on operating results or cash flows in the periods for which that determination is made and in future periods after the determination. In addition, future period earnings may be adversely impacted by litigation costs, settlements, penalties or interest assessments.
We are currently involved in several audits and adjustment-related disputes, including related litigation. This includes litigation in the United States District Court for the Western District of Michigan regarding our fiscal years ended June 27, 2009, June 26, 2010, June 25, 2011, and June 30, 2012. The United States District Court for the Western District of Michigan has scheduled a trial date in late May 2020 in response to our complaint filed on August 15, 2017 to recover $163.6 million of Federal income tax, penalties and interest assessed and collected by the IRS. Additionally, the IRS has proposed adjustments regarding the deductibility of interest for the years ended June 29, 2013, June 28, 2014, and June 27, 2015 and the IRS has proposed adjustments regarding litigation costs and transfer pricing positions for Athena Neuroscience, Inc. ("Athena"), a subsidiary of Elan acquired in 1996, for the years ended December 31, 2011, December 31, 2012 and December 31, 2013. We are also involved in litigation with Irish Revenue for the years ended December 31, 2012 and December 31, 2013.
On August 22, 2019, we received a draft NOPA from the IRS with respect to our fiscal tax years ended June 28, 2014 and June 27, 2015, relating to the deductibility of interest on $7.5 billion in debts owed to Perrigo Company plc by Perrigo Company, a Michigan corporation and wholly-owned indirect subsidiary of Perrigo Company plc. The debts were incurred in connection with the Elan merger transaction in 2013. The draft NOPA would cap the interest rate on the debts for U.S. federal tax purposes at 130.0% of the Applicable Federal Rate (a blended rate reduction of 4.0% per annum from the rates agreed to by the parties), on the stated ground that the loans were not negotiated on an arms'-length basis. As a result of the proposed interest rate reduction, the draft NOPA proposes a reduction in gross interest expense of approximately $480.0 million for fiscal years 2014 and 2015. If the IRS were to prevail in its proposed adjustment, we estimate an increase in tax expense for such fiscal years of approximately $170.0 million, excluding interest and penalties. In addition, we would expect the IRS to seek similar adjustments for the period from June 28, 2015 through December 31, 2019. If those further adjustments were sustained, based on our preliminary calculations and subject to further analysis, our current best estimate is that the additional tax expense would not exceed $200.0 million, excluding interest and penalties, for the period June 28, 2015 through December 31, 2019. We do not expect any similar adjustments beyond December 31, 2019 as proposed regulations, issued under section 267A of the Internal Revenue Code, would eliminate the deductibility of interest on this debt. We strongly disagree with the IRS position and will pursue all available administrative and judicial remedies. No payment of any amount related to the proposed adjustments is required to be made, if at all, until all applicable proceedings have been completed.
Following receipt of the draft NOPA, Perrigo provided the IRS with a detailed written response on September 20, 2019. That submission included an analysis by external advisors that supported the original interest rates as being consistent with arms'-length rates for comparable debt and explained why the exam team's analyses and conclusions were both factually and legally misguided. Based on discussions with the IRS, we had believed that the IRS staff would take our submission into account and meet with us to discuss whether this issue could be resolved at the examination level. However, in the weeks following such discussions, IRS staff advised that they would not respond in detail to our September submission or negotiate the interest rate issue prior to issuing a final NOPA consistent with the draft NOPA. Accordingly, we currently expect that we will receive a final NOPA regarding this matter that proposes substantially the same adjustments described in the draft NOPA.
On April 26, 2019, we received a revised NOPA from the IRS regarding transfer pricing positions related to the IRS audit of Athena for the years ended December 31, 2011, 2012 and 2013. The NOPA carries forward the IRS's theory from its 2017 draft NOPA that when Elan took over the future funding of Athena's in-process research and development after acquiring Athena in 1996, Elan should have paid a substantially higher royalty rate for the right to exploit Athena's intellectual property, rather than rates based on transfer pricing documentation prepared by Elan's external tax advisors. The NOPA proposes a payment of $843.0 million, which represents additional tax and a 40.0% penalty. This amount excludes consideration of offsetting tax attributes and potentially material interest. We strongly disagree with the IRS position and will pursue all available administrative and judicial remedies, including potentially those available under the U.S. - Ireland Income Tax Treaty to alleviate double taxation. No payment of the additional amounts is required until the matter is resolved administratively, judicially, or through treaty negotiation.
On October 30, 2018, we received an audit finding letter from the Irish Office of the Revenue Commissioners ("Irish Revenue") for the years ended December 31, 2012 and December 31, 2013. The audit finding letter relates to the tax treatment of the 2013 sale of the Tysabri intellectual property and other assets related to Tysabri to Biogen Idec from Elan Pharma. The consideration paid by Biogen to Elan Pharma took the form of an upfront payment and future contingent royalty payments. Irish Revenue issued a Notice of Amended Assessment ("NoA") on November 29, 2018, which assesses an Irish corporation tax liability against Elan Pharma in the amount of €1,636 million, not including interest or any applicable penalties.
We disagree with this assessment and believe that the NoA is without merit and incorrect as a matter of law. We filed an appeal of the NoA on December 27, 2018 and will pursue all available administrative and judicial avenues as may be necessary or appropriate. In connection with that, Elan Pharma was granted leave by the Irish High Court on February 25, 2019 to seek judicial review of the issuance of the NoA by Irish Revenue. The judicial review filing is based on our belief that Elan Pharma's legitimate expectations as a taxpayer have been breached, not on the merits of the NoA itself. The High Court has scheduled a hearing in this judicial review proceeding in April 2020, and we would expect a decision in this matter in the second half of 2020. If we are ultimately successful in the judicial review proceedings, the NoA will be invalidated and Irish Revenue will not be able to re-issue the NoA. The proceedings before the Tax Appeals Commission have been stayed until a decision on the judicial review application has been made. If for any reason the judicial review proceedings are ultimately unsuccessful in establishing that Irish Revenue's issuance of the NoA breaches our legitimate expectations, Elan Pharma will reactivate its appeal to challenge the merits of the NoA before the Tax Appeals Commission.
We regularly assess the likelihood of adverse outcomes resulting from tax examinations to determine the adequacy of our tax reserves. We believe that, based on a review of the relevant facts and circumstances, this matter will not result in a material impact on our consolidated financial position, results of operations or cash flows. However, while we believe our position to be correct, there can be no assurance of an ultimate favorable outcome, and if the matter is ultimately resolved unfavorably it would have a material adverse impact on us, including on liquidity and capital resources. We will consider the financial statement impact of any additional facts as they become available.
In addition, going forward, uncertainty regarding the future outcome of tax disputes such as the NoA or draft or final NOPA may have an adverse impact on our strategy and the results of such tax disputes may have an adverse impact on our financial condition and liquidity.
At this time, we cannot predict the outcome of any audit or related litigation. Unfavorable developments in or resolutions of matters such as those discussed above could, individually or in the aggregate, have a material impact on our Consolidated Financial Statements in future periods (refer to Item 8, Note 15 for further information related to uncertain tax positions and ongoing tax audits and Item 8. Note 17 for further information related to legal proceedings). In addition, an adverse result with respect to any of these matters could ultimately require the use of corporate assets to pay assessments and related interest, penalties or other amounts, and any such use of corporate assets would limit the assets available for other corporate purposes.