The DWP is required by law to send a reminder to the claimant to be received during week 3 of the 4 weeks normally allowed for the completion of the claim/review form.
The lead time to produce this letter is quite long so it is not unusual for claimants to receive a copy even though they have already returned the form.
I would still contact the DWP to confirm receipt of your form but I hope the above offers some reassurance that things have not gone amiss with your claim.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems
The following user(s) said Thank You: denby, Gary, LL26