If you or your company is moving to or conducting business in a foreign country, then you will need all official documents to go through a document authentication service or an Apostille process. This process is a one-step certification that takes place at the level of government in which the document originated. For example, a notarized state document will be certified by the Secretary of State in the state that it was notarized in and a federal document, like an IRS Form 6166 to prove US tax residency, would get certified at the U.S Department of State for apostille. Resource

Can You Apostille IRS-Issued Documents? Here’s the Answer

For documents that are to be used abroad, an apostille is a certification that confirms the authenticity of the signatures and seals on the document. This process ensures that a document will be accepted in any country that is a member of the 1961 Hague Convention on the Legalization of Documents. The apostille also identifies the country where it was issued.

In the case of an apostille for IRS documents, this is a certification that confirms the accuracy of the IRS tax forms that you or your company filed with the IRS. Most often, you will need an apostille for IRS Form 1099 documents that verify the payments you or your company received from others.

If you are going to need apostilles for your IRS documents, then I would suggest that you start by requesting the transcripts online through the IRS and researching your state’s apostille processes simultaneously so that you can be ready to take your completed forms to the secretary of state’s office for apostille as soon as they are completed.