Yes, the Record information can be exported in a variety of formats. Excel, comma delimited, PDF.
For simplicity, why not just Save A Copy of the database each month? You could delete previous invoices in the CopyOct2012 database after saving it.
It can be done immediately without any coding or scripting...
The thing is that the database has already too many records, I´ve already exported the records that I made the last 3 months and that was easy because they were all the records in the database but now I want to say Save all the records from October or from November.
But the difficult thing is that my database was constructed with one tabl for invoices and from that table it goues to the governent table, the water company, road construction company and normal customers table. each table has different information...
I´ll show you with the picture...
I don't speak or read your language so what I can deduce from your screen shot is quite limited, but what I see here strongly suggests that you should restructure your database.
From such a structure, you can perform a find on a layout based on LineItems for all goods and/or services sold in a given date range and then you can export to csv, Excel or other file format data in a table form where each row lists a single product or service with additional columns listing data from the Invoices and Clients table to complete the data set.