Complete your form before you go to photocopy your utility bills and then take a copy of your completed form as well so you have a record of how you filled it in if there are any queries.
Note the date you posted the forms on the top of the application form copy you have kept.
Compare copies of your old bills with new bills after the allowances have been awarded to ensure that the reductions have been applied. If they do not appear, contact the utility directly to check the account.