If you use the Belbo cash register system, you can enter expenses and sell vouchers. These always have sequential numbers.
Your Belbo cash register system ensures that the sequential numbers of vouchers or expenses never appear twice. However, it can happen that numbers appear to be missing. This is for technical security reasons.
Voucher numbers
If a voucher is entered in the cash register process but then deleted, the number of this voucher is not reassigned. Vouchers that are added to a cash register process but are not subsequently cashed out also receive their own numbers, which then do not appear in the voucher list. This ensures that even when using the Belbo cash register from multiple devices or by customers in the voucher shop, numbers are never assigned twice and each number can be uniquely assigned to a voucher.
Receipt numbers
Since 1.1.2021, a new receipt number is blocked for each reversal. This is necessary to comply with the legal requirements that come into effect from 1.4.2021 and with the use of the TSE.
If an already cashed booking is reversed, both the reversal receipt and the new receipt are assigned new receipt numbers. This can always be determined in the cash register process under "History":

Finding receipt numbers
You can also find reversed receipt numbers via the cash register using the search function:

Expense numbers
Cancellation or reversal of an expense
If an expense is entered in the cash register system but then deleted, the number of this expense is not reassigned. Even if the entry of an expense is started but the process is not completed, the system assigns a number which is then not reassigned. This ensures that even when using the Belbo cash register from multiple devices, numbers are never assigned twice and each number can be uniquely assigned to an expense receipt.
Automatic cash withdrawal
If you have activated the "Automatic cash withdrawal" function, a change withdrawal may be automatically posted at the end of the day. These postings also use expense numbers which are then no longer available. These expense numbers are listed in the DATEV export and can thus be traced by the tax office.