Yes, absolutely - most sole traders and small businesses invoice for months or years before ever registering for VAT, and there is nothing irregular about it. You simply do not charge VAT, and your invoice does not show a VAT number, VAT rate, or VAT amount anywhere.
What a non-VAT-registered invoice needs
A unique, sequential invoice number
Your business name (or your own name and any trading name) and address
Your customer's name and address
A clear description of the goods or services provided
The invoice date and date of supply
The total amount due - with no VAT breakdown, since none is being charged
The one thing you must never do
Never show a VAT number or add VAT to an invoice if you are not VAT registered - this is a genuine legal issue, not just a formatting mistake, since it misrepresents your VAT status to HMRC and to your customer (who may try to reclaim VAT that was never legitimately charged).
Should you mention you are not VAT registered?
You don't have to state it explicitly - the simple absence of a VAT number and VAT breakdown already tells a VAT-registered customer everything they need to know. Some small businesses add a line like "Not VAT registered" purely to pre-empt the question, but it is optional, not required.
When this changes
The moment you register for VAT - whether because you crossed the threshold or chose to register voluntarily - every invoice from your effective registration date needs your VAT number, rate and amount. There is no transition period; the very next invoice after your effective date has to be a full VAT invoice.
Invoito works exactly the same either way - VAT is simply switched off in your business settings until you register, at which point turning it on adds the right details to every invoice from that point automatically.
Do I need a VAT number to send an invoice?
No. Most UK sole traders and small businesses send invoices without VAT for months or years before ever registering - a VAT number is only needed once you are VAT registered.
Can I add VAT to an invoice before I am registered?
Should I tell customers I'm not VAT registered?