Company · OSBC · CIK 357173

Old Second Bancorp Inc (OSBC) SEC filings and CIK.

OSBC’s SEC Central Index Key (CIK) is 0000357173, or 357173 without leading zeros. The SEC’s ticker file lists it as OLD SECOND BANCORP INC.

Ticker: OSBC
CIK: 0000357173
Other tickers: None
Insider transactions, Q3 2026: 15

Insider trading

In Q3 2026, insiders at Old Second Bancorp Inc reported 15 non-derivative transactions on 14 Forms 3, 4 and 5, including 0 open-market purchases and 7 sales. See every OSBC insider transaction →

Recent filings we observed

From our record of EDGAR’s latest-filings feed and sampled daily indexes. Not a complete filing history; use the filings API for that.
Filed	Form	Accession
2026-10-30	SCHEDULE 13G	0002100119-26-001679

Get OSBC SEC data through the API

Filing history

curl "https://sec-api.dev/api/v1/filings?cik=357173&limit=10" \
  -H "Authorization: Bearer $SEC_API_KEY"

Company profile

curl "https://sec-api.dev/api/v1/companies/357173" \
  -H "Authorization: Bearer $SEC_API_KEY"

Reported XBRL facts

curl "https://sec-api.dev/api/v1/facts/357173?taxonomy=us-gaap&concept=Revenues&limit=10" \
  -H "Authorization: Bearer $SEC_API_KEY"

Ticker to CIK API · SEC filings API · Old Second Bancorp Inc on SEC.gov

Questions

What is OSBC’s CIK number?

OSBC’s SEC Central Index Key (CIK) is 0000357173, or 357173 without leading zeros. The SEC’s ticker file lists it as OLD SECOND BANCORP INC.

How do I find Old Second Bancorp Inc’s 10-K?

Request /api/v1/filings?cik=357173&form=10-K, or open the company’s EDGAR page and filter by 10-K. Foreign issuers file 20-F or 40-F instead.

Ticker and CIK: SEC company_tickers.json, cached 2026-11-02. Tickers can move between entities; the CIK identifies the filer.

Plain-text version for agents and LLMs: /companies/osbc.md

Independent. Not affiliated with, endorsed by, or sponsored by the U.S. Securities and Exchange Commission. Data is reproduced from public SEC filings and datasets. Not investment advice.