Final answer:
Jackie's unreported salary from her Form W-2 would have been identified by the IRS's Information Matching program. This program compares taxpayer-supplied information on tax returns with data provided by employers and institutions to identify discrepancies. The correct option is C.
Step-by-step explanation:
The IRS program that likely identified Jackie's oversight of not reporting her salary from her Form W-2 on her tax return is the Information Matching program. This program cross-references the information reported by taxpayers on their tax returns with the information provided by employers, financial institutions, and other third parties.
If there is a discrepancy, such as missing income, the IRS will flag the return for further review, which can lead to an audit. The DIF System is used to score the potential for underreported or overreported items based on a formula, while Document Perfection involves checking tax returns for mathematical and clerical errors, and the Mathematical Correction program corrects basic math errors on a return.