As BM & ubasses sensibly say your business status makes no difference to how long you may wait for an invoice to be settled. Many companies have only one payment day per month and will deal with all approved invoices from the previous month on that day regardless of what terms the supplier has applied, if you wish to obtain further orders from the same source you will have to accept this, if you take legal action you can probably say you will never deal with that company or individual again, it may be unfair but it is true. The only way to be paid on time is to chase payment on a daily basis as soon as they become overdue and hope you do not irritate the supplier over much, if you require repeat business.