Start Month of a Financial Year

@Tsuyoshi_Inoue 

This is a really good use-case for demonstrating the DISCO methodology.

The only ambiguity with this question though is what you meant by "current period".  I'm assuming that current period is the same for all clients.

In short, I would suggest the following (please let me know if you need a detailed example).

1. Create a "time range" that spans the length of your transaction module
2. In a separate system module calculate the "current year" using the "current period". use the START() function.
3. Create a system module that uses that time range. Set the line times to "year". 
4. Create "date" line items in that system module that reads the "current year" using the START() and END() function.
5. Create another system module that uses your transaction module ID. 
6. Create a Boolean called "Invoice Include?" which is references the valid start and end dates you created above.
7. Filter your transaction module using this Boolean. Now only the invoices that are related to the year you want will be shown.

If the current period is different by client, then you'll need to add client to your system module and calculate each client's year separately. The filter will by client as well.

Kind of an advanced topic but very doable in Anaplan.