One of the more common errors I have seen with single-member LLCs (aka \"Checkbook IRA\") in an IRA is the use of an incorrect TIN for an investment. When you make a direct investment (IRA or taxable) in a fund or syndication you are required to provide a TIN on the subscription agreement (sometimes a W-9 is required as well). In the case of an investment using a SDIRA, the custodian should have procedures in place to make sure the correct TIN is shown before they execute the subscription agreement on behalf of your IRA. This prevents the IRS from sending you a letter stating that you under-reported the gain/income for the tax year in which it occurred. This same TIN should be used when making an investment from your Checkbook IRA or Trust IRA.