The first order of each trading day is #101, and every order after it goes up by one. Numbers are always three digits: after #999 the count goes back to #101.
When the numbers start again
Order numbers start again at #101 at 4am, not at midnight. If you trade past midnight, orders taken between midnight and 4am carry on from that evening's numbers. Your first order the next day is still #101.
The 4am change uses your store's time zone, so it moves with the clocks in spring and autumn.
Every till shares one count
All your tills, your website, your app, your kiosk and Delivery Platforms orders share the same count. Two orders can never get the same number on the same day, even if two tills take an order at the same moment.
Can I choose a different starting number?
No. Every store starts at #101. The old First Order Number setting under Setup > POS > Receipts has been removed, because it no longer changes the numbering.
Why are some numbers missing?
A number is given to an order as soon as the first item goes into the basket. If a customer starts a basket on your website or app and leaves without paying, that number is not used again. You may see small gaps, for example #104 followed by #106. Nothing has gone missing.