I was recently audited by the IRS for my 2016 taxes which I claimed $1,000 for the American Opportunity Credit. Can I defend this simply by sending them my 1098-T?

[DanO]

The 1098-T is very important, but you should also have evidence that you were enrolled and that you paid the amount of qualified tuition and related expenses before taking the credit.

This is from the IRS:

What should I do if I receive a letter from the IRS or I’m audited? Taxpayer rights

You will benefit from knowing your rights as a taxpayer and being familiar with the IRS's obligations to protect them. The goal of the Taxpayer Rights Corner is to inform you of your rights during every step of your interaction with the IRS.

Did you receive a letter?

If you receive a letter or are audited by the IRS, it may be because the IRS did not receive a Form 1098-T, Tuition Statement, verifying the student’s enrollment. Or, we need additional information to support the amounts of qualified expenses you reported on Form 8863. Review your Form 1098-T to make sure the student’s name and social security number are correct. If they do not match, contact the school to correct the information for future 1098-T reporting. If the student should have and did not receive the Form 1098-T, contact the school for a copy. Note: There are a few exceptions in which educational institutions are not required to furnish Form 1098-Ts. For details please see “What is Form 1098-T, Tuition Statement and how do I get it?”

If you claimed expenses that were not reported on the Form 1098-T in Box 1 as amounts paid or if your school reported the amount you were charged for qualified expenses in Box 2, please send us copies of paid receipts, cancelled checks or other documents as proof. See your letter for further instructions for what documents to send. If you do not have the letter, see our page Forms 886 May Help You for the Forms 886-H-AOC and 886-H-AOC-MAX for examples. Form 886-H-AOC is also available in Spanish.

Audit and examination process

IRS selects income tax returns for examination identified by computer programs showing a return has incorrect amounts. The examination may or may not result in a change to your tax or credits.

Use the following links for additional information:

Pub 3498-A, The Examination Process (Examinations by Mail) (PDF)
Pub 556, Examination of Returns, Appeal Rights, and Claims for Refund (PDF)

[Critter]

Q22. I received a letter from the IRS questioning my AOTC claim. What should I do?

A22. If you receive a letter or are audited by the IRS, it can be because the IRS did not receive a Form 1098-T, Tuition Statement, or the IRS needs additional information to support the amounts of qualified tuition and related expenses you reported on Form 8863. 

If you did receive a Form 1098-T review it to make sure the student’s name and social security number are correct. If either is not correct, contact the school and ask the school to correct the information for future 1098-T reporting. If the student should have, but did not receive the Form 1098-T, contact the school for a copy.

Please note as described above, there are exceptions in which eligible educational institutions are not required to provide a Form 1098-T. See Q&A 18 for more information about the Form 1098-T. 

If you claimed expenses that were not reported on the Form 1098-T in Box 1 as amounts paid or if your school reported the amount you were charged for qualified tuition and related expenses in Box 2, please send the IRS copies of receipts, cancelled checks or other documents as proof of payment. See your letter for further instructions for what documents to send.  

https://www.irs.gov/credits-deductions/individuals/education-credits-questions-and-answers