A summons with an endorsed complaint is a document that combines a summons and a complaint into a single document, rather than having two separate documents, and is normally used in simple debt collection cases.
The deadline for responding normally appears on the face of the summons.
The first issue that an attorney should address is the practical one:
when is the answer due? CPLR §320 prescribes the time periods for when
a responsive pleading must be served. This is generally 20 or 30 days
from completion of service (20 days when service is by personal
delivery to the defendant within New York State, 30 days all other
times). Service is not always complete when the papers are delivered
by the process server. This is especially so when service is
effectuated through substituted service (leaving the summons and
complaint with someone of suitable age and discretion with follow-up
mailing CPLR §308). In such a situation, service is complete ten days
after the filing of the proof of service (the summons and complaint
together with an affidavit of service is known as “proof of service”)
with the court. The time periods for other methods of service are
provided for in CPLR Article 3 and, in the interest of brevity, will
not be discussed here.
You need to file a timely answer or motion in lieu of an answer by the deadline set forth in the summons. Generally, this is best to have a lawyer handle for you but some of the many considerations involved are set forth here (this is the source of the block quote above). They include, admitting or denying each allegation, asserting affirmative defenses, raising any available objects to jurisdiction, venue or service, making a jury demand, paying a filing fee, and asserting any counterclaims or crossclaims.
If you do not respond by the deadline a default judgment will be entered against you.