IL SB1379

Requires taxpayers of income-producing property to submit annual income and expense data to county assessment officers in counties with 3,000,000 or more inhabitants by July 1 each year.

Allows county boards in smaller counties to adopt resolutions requiring income and expense data submission by March 30 each year, with income-producing property defined as non-exclusively owner-occupied property generating income but excluding properties valued at $100,000 or less, residential properties with 6 or fewer units, farmland, and state-assessed properties.

Imposes a penalty of 0.05% of prior year's market value (capped at $100,000 per property) plus 0.05% monthly interest if taxpayers fail to submit required data within 60 days of notice from the assessment officer.

Protects personal data including social security numbers and tax forms from disclosure under the Freedom of Information Act, but allows disclosure of compiled and anonymized income and expense data, with violations classified as a Class B misdemeanor subject to fines up to $7,500.

Directs that 75% of collected penalties and interest revenue benefit the assessment officer's office and 25% benefit the county general fund.