Which Bednobs is an utter piece of nonsense and a ridiculous tactic almost always used to delay paying usually smaller suppliers by usually bigger customers who know the supplier cannot afford to tell them to "do one".
An invoice should clearly state your name and address, and business name if that's different. If it's a company it should name the directors and company registered number. It should have a date and an individual number, a VAT Registration number (if applicable) and if it relates to work carried out on a specific earlier date then that should be noted in the detail. If the customer gave a purchase order number then quote that on the invoice. Include a brief description of the work done and the price thereof. If VAT registered then a clearly separately identifiable VAT charge and then a total. If not VAT registered then it should make it clear that the business isn't VAT registered and no Input VAT is included in the charge. It should state the expected payment terms ie within 30 days or by end of calender month following, whatever you agreed or believe appropriate.
That's it. It doesn't need anything else and if all that is included then it's nobody else's business but yours how it looks, though of course in practice if you want paying by some companies you will have to fit in with their demands. You may or may not want to give it some colour or a business logo.