The IRS requires taxpayers to report cash transactions over 10k. If it is in the form of a deposit or wire transfer to the bank, the IRS will automatically get a report of it from the financial institution.
If the transaction is legitimate, such as a loan or for a business purpose, it would be a good idea to keep good records in case the IRS sends a letter asking questions about it.
How do you report cash transactions? You should report it using a Form 8300. It can also be reported online through the BSA Efiling System. A link to that system can be found here.
https://bsaefiling.fincen.treas.gov/main.html
If you receive more than 10k in one lump sum, in two or more related payments within 24 hours, as part of a single transaction within 12 months or as part of two or more related transactions within 12 months, it must be reported on Form 8300.
What is considered a “cash” transaction? coins and currency of the US or a foreign country. Cashier’s check, bank draft, traveler’s check or money order.
When do you file ? 15 days from when you received the cash if you receive more than 10k up front. Otherwise, you report it when you exceed 10k or more.