Can someone tell me how to register for online voting as they are asking for a 10 digit security code & mine 14 digits confused.com

Sorry ... Did mine by text

Where are you getting that from?

I used this site:

https://www.gov.uk/register-to-vote

And it only asked for name, address, DOB, NI number.

I filled my elderly brother's in and then just posted it as he is a technophobe and doesn't believe in computers or iphones.