We’ve found that Experian will not investigate any dispute letters that are not signed by the consumer. Only Experian requires a signature on the dispute letters. TransUnion and Equifax do not require your signature when disputing. When downloading the Dispute Signature Template, you’ll notice that there aren’t any disputes on this Template. Instead, we create your custom disputes and then merge them into a copy of this signed Template, which is then mailed to Experian on your behalf.