Can't help you with an invoice but for the inspection sheet just use Excell.
Put Date at the top of one collum, Observations at the top of the next, Action required on the next, Action completed on the next and initials on the last one.
Then just put in the dates you check (or checked
) your ladders, any problems noticed, any repairs needed such as the feet changed and if so when theat was done and signed to say all ok...... A good Idea is to check your ladders either every Monday or every Friday. If nothing needs doing then just put in AOK and your initials in the siged collum. Then just email it back to them.
Regards
Mr H