Is the work operational before you issue an invoice?
As a licensed plumber, you give a quote for the installation of 10 toilets and this is considered to be a single transaction.
The quote is accepted and you commence work. Each toilet becomes operational in turn over a period of five days.
The work is considered to be completed after the tenth toilet becomes operational on the fifth day. An invoice is issued a week later.
As all of the work covered by the single transaction becomes operational prior to an invoice for the work being issued, a Form 4/4A must be submitted to the QBCC within 10 business days of the fifth day.