For about 30 years I have done business as a sole proprietorship with an EIN. Every year clients send me 1099s and I report the income on Schedule C.
About 20 years ago I changed the business' name. (The old name was four unpronouncable initials, the new name is the slightly more pronouncable name of a nearby waterfall.) I filed the required DBA with the county and use the new name. The Sched C says "old name/new name" and the IRS has always accepted that.
Now clients are telling me that my new business name fails the IRS' TIN match, presumably because 30 years ago I got the EIN with the old name. I cannot get a new EIN, only one per person allowed no mater how many sole proprietorship businesses you have. So how do I tell the IRS that the business with the EIN now has a different name?