A deadline works because it forces a decision now instead of an indefinite "someday," but it only works when the reader believes it's real.
Tie the Deadline to a Genuine Reason
A deadline explained by an actual constraint, like limited capacity or a real enrollment window, is more credible than an arbitrary countdown.
Be Consistent With Past Deadlines
A deadline that turns out to be extended repeatedly teaches readers to ignore future deadlines from you entirely.
State What Happens After It Passes
Clearly explaining the consequence of missing the deadline, whether it's a price increase or the offer closing, makes the urgency concrete rather than abstract.
Next step: Use the Sales Letter Writer to draft a deadline section explained by a genuine, credible reason.