It is not unwise at all to contact IRS if one believes that they have unpaid taxes. In 2012, the IRS has made some changes on handling expat tax returns, giving them “a series of common-sense steps to help U.S. citizens abroad get current with their tax obligations and resolve pension issues,” for “(a)ny taxpayer claiming reasonable cause for failure to file tax returns, information returns, or FBARs.” Besides, not paying taxes may have civil and criminal consequences; this is why it is better to “come clean” and contact the IRS regarding the delinquent payments.

However, before doing so, it is usually more advisable to work with an expert CPA, or better yet, a tax attorney, in order to be guided on what to do and be well-advised on the laws regarding taxes and payment.