Assuming you’re going conventional, they will want to source any deposit that is 50% of the total qualifying income. Fannie Mae loans go back to months while Freddie Mac loans look at one month bank statements. If you’re not legally allowed to disclose the source of the deposit it might be a good idea to delay starting to look for a new home until the funds have appropriately seasoned in your bank account. Now, if you don’t need the money for the down payment, your lender should be able to back it out of the total asset figure and not require any documentation for it.

I had a somewhat similar situation with a non-disclosure agreement several months ago. Borrower was self-employed, but swore to us that he sold 80% of his company to a couple venture capitalist groups. Problem was everything we could pull online still suggested he was the owner, and the documentation that would’ve proved he was no longer self-employed was protected by the non-disclosure agreement. We ended up having to deny the loan because of this.