This is the 3860th most frequent German word.
spätestens
"Spätestens" means "at the latest."
In this sentence, 'spätestens' sets a latest deadline for when the described action (starting the work) will commence.
Ich werde spätestens morgen mit der Arbeit beginnen.
I will start the work by tomorrow at the latest.
Here, 'spätestens' establishes the ultimate time limit for sending the document, indicating urgency or deadlines.
Bitte schicken Sie mir das Dokument bis spätestens Freitag.
Please send me the document by Friday at the latest.
In this context, 'spätestens' specifies the fixed final time by which departure should occur.