Almost no jurisdiction requires a signature for an invoice to be valid, which raises a fair question: why bother? The answer has less to do with legal necessity and more to do with how the document actually lands with the person reading it.
It signals a real person stands behind the document
A signature, even a simple one, makes an invoice feel like it came from a specific person rather than an anonymous system — a small psychological shift that matters more for new clients who haven't worked with you before.
It's a habit borrowed from formal paperwork
Contracts, official letters, and formal agreements almost always carry a signature — adding one to an invoice borrows that same sense of formality and intentionality, even though it isn't strictly required.
It's a small, low-cost differentiator
Plenty of competitors send generic, unsigned invoices generated by whatever software they use. A signed invoice, even with a simple digital signature, stands out slightly as more personal and considered.
It's especially worth doing for larger invoices
On smaller, routine invoices it matters less. For a large project invoice or a first invoice to a new client, the extra touch of a signature can reinforce that the amount and details were personally reviewed, not just auto-generated.
Keep it simple and consistent
The same signature used on every invoice, placed in the same spot, looks intentional rather than like an afterthought added to just one document.