The custodian is the trustee for your client's IRA. That would be their EIN. The retirement account is tax exempt normally. There was an >$1,000 event that doesn't qualify. Your client should know about their own investments.

The tax, if any, would have been paid from that IRA and reduces the value of the IRA account. Think of this as getting a net value from that investment: profit or gain or earnings minus the tax.