The set

An invoice is rarely the only document

The same job usually produces three or four pieces of paper, and they have to agree with each other.

A quote goes out before the work. A purchase order comes back confirming it. An invoice follows the work. A receipt follows the payment. Each is a different document with different fields, and using an invoice template for all four is how numbers stop matching.

The value is less in any single form than in them sharing a layout. A client receiving your quote and then your invoice sees the same document family twice, which is a quiet signal that someone is paying attention.