1. Setting Financial Year
To set the financial year for your business, go to Business Settings > Accounting & Inventory > Taxation and Billing > Financial Year.
You can either select the dates manually OR you can just choose from the pre-set periods as shown in the image above.
2. Reset Document Serial Numbers
If you want to reset the document serial numbers, go to Business Settings > Accounting & Inventory > Custom Labels and Fields > Reset Document Serial Numbers.
This will reset serial numbers for all your future invoices and other accounting documents.
Important Note:
Once you reset the document serial numbers from the settings, It will not automatically reset the number series for you. You will have to manually change it in the first document.
For example,
Say before resetting the number series, your last invoice number was A00997.
Now, after resetting the series, If you create a new invoice, it will automatically show the invoice number as A00998.
This doesn't mean that reset did not work. You can simply click on the invoice number and change it to A00001.
You will only have to do this manually once. After that, the system will automatically number your invoices based on the new series.