Multiple names

[Yoly]

I have a taxpayer that multiple last names there too long.  I'm trying to do an extension and it will not take it because it's asking for the name on the SSN I have tried a various ways of entering but it still rejects the extension.  Is there a way of increasing the number of characters or is there another way of entering their names???

[TaxGuyBill]

I think the IRS just matches the first 4 letters in the last name, so as long as that is correct, you can probably enter any last name you want.

[taxes96786]

Is this a new client? do you have a copy of last efiled return? Use the name as it appears on that return.