A unique identifier, date, and invoice number are essential elements on an invoice. Any invoice without these elements is considered inadequate and unsuitable for use. The inclusion of these elements onto the invoice has become easier with time as specialized software is available to assist with the creation of a typical invoice.

Invoice Identifiers

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Unique Identifier

A unique identifier is an alphanumeric or numeric code that is used to catalog items or services that are offered by a business. Some applications give you the option to either select from the preexisting template of codes or allow you to general your own codes. For example, considering the invoice generated by AA Associates, codes ASD001, ASD013, and ASD006 are codes that are connected with a pack of pencils, a pack of pens, and a ream of paper, respectively.

Therefore, when you are generating an invoice for your company, the moment you input your unique identifier code, the software automatically fills the description and unit price sections with information that is associated with that particular code. For example, selecting ASD001 auto-fills the invoice template with a description of a pack of pencils and a unit price of $30 per pack.


The date is written to help with documentation. It tells the buyer when an invoice was generated and further validates the legality of the document. Most invoice generating applications automatically input the date that corresponds to the date you create an invoice. However, you are giving the option to input your desired date manually especially if the invoice you are generating is going to be used in the future.

Invoice Number

In most cases, invoice numbers are generated by the invoice generating software. However, you mostly get the option to input your customer number if you have any company format that you may wish to implement. Additionally, some applications give you the opportunity to cascade the date of shipment into the invoice number for every shipment.