If a party that has obtained a Judgement by default and then fails to meet a deadline set by the Judge regarding the amount their claim is for, what happens or can happen next?
I assume you mean that the JiD was for an unspecified sum with the amount to be decided? Presumably directions were issued for filing and serving of evidence?
If that has not been done, the claim can be struck out. However, given that Judgement has already be obtained it would be a harsh sanction and the Claimant could apply for a extension to the time limit for service of the documentation if he has a good reason for his failure.