The Deadline — and How to Get More Time
Return the form by the date printed on the letter — normally around four weeks from the date it was sent. Use the printed date; that's the one that counts.
Not returning it without good reason can lead to a decision that you don't have limited capability for work — which affects your Universal Credit. If you need more time (waiting for medical evidence, unwell, need help filling it in), phone the number on the form before the deadline and ask — extensions for good reason are routine. Keep a note of the call.