Hi, I recommend your son contact the retail customers who paid the carpet shop, ... and request a copy of their paperwork... then re-issue his invoices with the correct contract number details and dates.
Alternatively, he could request to see the master book, and find the details within this book.. which holds the master copy, and obtain the details for this..
On the invoices your son re-generates, he needs to add the following words, assuming no more than 6 months has past.. since the work was completed..
"This is a payment claim made pursuant to ....
BUILDING AND CONSTRUCTION INDUSTRY SECURITY OF PAYMENT ACT 2009"
BUILDING AND CONSTRUCTION INDUSTRY SECURITY OF PAYMENT ACT 2009 - SECT 13
(1) A person referred to in section 8 who is or who claims to be entitled to a progress payment (the "claimant") may serve a payment claim on the person who, under the contract concerned, is or may be liable to make the payment.
(2) A payment claim—
(a) must identify the construction work (or related goods and services) to which the progress payment relates; and
(b) must indicate the amount of the progress payment that the claimant claims to be due (the "claimed amount"); and
(c) must state that it is made under this Act.
(3) The claimed amount may include an amount—
(a) that the respondent is liable to pay the claimant under section 28(3); or
(b) that is held under the construction contract by the respondent and that the claimant claims is due for release.
(4) A payment claim may be served only within—
(a) the period determined by or in accordance with the terms of the construction contract; or
(b) the period of 6 months after the construction work to which the claim relates was last carried out (or the related goods and services to which the claim relates were last supplied),
whichever is the later.
(5) A claimant cannot serve more than 1 payment claim in respect of each reference date under the construction contract.
(6) However, subsection (5) does not prevent the claimant from including in a payment claim an amount that has been the subject of a previous claim.