The Principal Laws Governing Electronic Invoices (e_Invoices or eBills) _ In Spain, Directive number 115 generally applies, although these regulations have also been reinforced in national policy, particularly in the following laws: Royal Decree number 1496 Billing Regulations.
Numbers and Numbers and Records and Books _ must be trackable Referring to "invoice #9048," rather than "That invoice I sent you last month, I think on a Tuesday," is much easier to track for both you and your client. Assign numbers to your invoices systematically, consistently and chronologically. Some people number their invoices by year (for example, 2009043 would be the 43rd invoice of 2009). You could also specify a code for the project. For example, ABC06 would be the 6th invoice for the ABC project that you're currently working on. Having an invoice and project numbering system keeps everything in line.
Invoice example With GST & PST An invoice not only shows the customer or client how much money is due but provides tax information, in some countries multiple taxes may apply, for example in Canada it is required to put the Supplier's identification numbers for GST and QST taxes purposes. Whenever a taxable sale is made, the customer must be informed that GST and QST are added to the selling price. As there are no standard invoices required by law for this purpose, you must indicate the amount of the taxes on the cash register receipt; on the invoice or contract remitted to the customer. If you choose to indicate the GST and the QST, the amounts must be stated clearly.The European Union requires a VAT (value added tax) identification number on invoices between entities registered for VAT.