Some products - such as concrete can not be re-sold to another customer if the intended one decides not to pay...it's not possible to collect it or accept a return.

Gates or furniture made to exact specifications can not always be re-sold to another customer as they are too bespoke to simply be re-packaged.

There is also the question of cashflow - if your business has to purchase materials in advance, it can be too much pressure on cashflow if the customer pays at the end of the task.  It can be important to send invoices for stage payments.  That way the customer pays in advance for materials bought in.

With regards to bookkeeping we are in a similar situation, we can not take our time back and so we are moving towards billing at the start of the month like the phone and utility companies do.  This means if necessary, money can be returned to the client however time can never be given back so it is a better fit for our business.

If you need help to get those invoices out to customers, to keep the cashflow under control, give BW Bookkeeping a call to see if we are a good fit to work together.