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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for IRS requirements:

EFILE: IRS requirement, often
EFILE: IRS requirement for many
SSNS: IRS requirements
SSN: IRS requirement
SSNS: The IRS requires them
TAXIDNUMBER: Business datum required by the IRS