Being helped by someone else
An interpreter, a witness, or a support worker can be recorded on the signature.
Before finishing, say that somebody helped you.
Enter their name and what they were there as: interpreter, witness, or support worker.
Sign as usual.
You should see
The completion record names the person who helped and what they were there as. This protects everybody — including them.
If it did not work
The role you want is not listed. Choose the closest one. A short fixed list means the record says what somebody was there as rather than leaving it to be guessed at later.