Morally you may well find it wrong, but this is capitalism and morality doesn’t come into it.

Having worked for a large company organising invoices for that department, then we processed our invoices on a monthly basis and which were then passed on to the accounts department for payment.

On average it would have taken two months for an invoice to be paid, so sometimes less, sometimes more.

Late payment is the bane of all businesses. There isn’t really a solution to it although at least web designers usual ask for a deposit first and then don’t hand over the final product until all invoices have been settled.