Hi,

Record the invoices from the prior fiscal year.
It is simple to say, but preparation through accounting, configuration, financial accounting, and new company financial setup is required before:
Include the previous fiscal year(s) when defining time periods.
Define the timeframes of this fiscal year or years.
Make sure your system for numbering invoices doesn't become disorganised. For both sales entry and purchase entry, you can change your invoice numbering in settings/configuration/Sequences & Identifiers/Sequences.
Make sure the correct date and time are used when you book your invoices. After that, be careful to renumber your invoices correctly for reservations made in the current year.

Hope it helps