A new year usually also means resetting the invoice numbering. It's nice if the first invoice of the new fiscal year starts with, for example, 001. This item explains how you can adjust the invoice numbering. If you don't want to change your numbering, you don't need to do anything.
By default, the numbering continues sequentially. In that case, the next consecutive number will be used for the invoice number of the new fiscal year. For example, if the last invoice number is 2023-378, the first invoice number of 2024 will be 2024-379. If you want the invoice numbering to continue like this, you don't need to take any action.
With a simple setting, you can ensure that the numbering starts with 2024-001. To do this, go to Settings -> Sales settings.
If you want to reset the invoice numbering and have the checkbox "Reset number series at the beginning of the new financial year" enabled, then you don’t need to do anything. The invoice numbering will automatically reset to 1.
Note: Make sure to do this before January 1st. Only then will the invoice numbering reset.
If you still want to create invoices for 2023 in 2024, that's not a problem. Just make sure that the option "Post invoices on draft date" is checked. This way, the invoice will have the invoice date you want, not the date of sending.
If you use recurring invoices and have the "Send automatically " checkbox enabled, make sure that you have set up the invoice numbering before 2024.