Greetings!
We filed a 2017 tax return for a personal client, and did so on paper because efile was not available for them. For one of their dependents, an additional letter was added to the child's last name in error. The child was the only one on the return with that last name, being the progeny of a union several marriages ago. IRS issued a notice disallowing the exemption because of the name spelling (according to the taxpayer). Instead of the taxpayer receiving their anticipated refund, they received a bill.
What is the best way to remedy this situation with IRS? Is an amended return required, or can it be done with a letter of explanation accompanied by supporting documentation?