Forms reporting income arrive in mailboxes each winter, but the taxpayer is the second recipient. The tax authority receives the same data and compares it to filed returns.
The information reporting system
Payers of certain income are required to file information returns describing what they paid and to whom, identified by taxpayer identification number.
Employers file wage statements, brokers report proceeds and dividends, banks report interest, and businesses report payments to independent contractors above a threshold.
Each of these is transmitted to the tax authority, building a file of reported income associated with a taxpayer before that taxpayer files anything.
How matching produces notices
After returns are processed, an automated program compares reported income from information returns against amounts appearing on the corresponding return.
Discrepancies generate a notice proposing an adjustment. The notice is a computer output, not the result of a person examining the return in detail.
This is why such notices sometimes propose changes that are plainly wrong, for instance counting gross proceeds from securities sales as though the entire amount were income.
Why the taxpayer identification number matters
Matching depends on the identification number attached to the payment. An incorrect number breaks the link and can leave income unmatched or attributed to someone else.
Payers collect certification of the number before payment, which is why a form requesting it precedes most contractor and account relationships.
Failure to provide a valid number can trigger backup withholding, where the payer withholds a portion of payments and remits it against the recipient's eventual liability.
What corrected forms do
Payers issue corrected information returns when errors are found, and brokers in particular reissue statements as underlying data from securities issuers is finalized.
A corrected form supersedes the original in the matching file, which is why filing early from a preliminary statement can produce a notice months later.
The correction process is why some institutions delay issuing statements until later in the season rather than sending an early version they expect to revise.
Where the system does not reach
Income without a reporting requirement never enters the matching file, which historically included many cash transactions and certain payment types.
Thresholds determine coverage, and payments below a stated amount often generate no information return even though the income remains reportable by the recipient.
The gap between what is reported by third parties and what is legally reportable is why compliance rates differ so sharply across categories of income. Rules and thresholds change over time and vary by situation, so a professional is the right source for a specific case.