It is not mandatory to change the invoice series at the beginning of a new financial year. The decision is entirely up to you. As long as your invoices are sequential and comply with tax regulations, you can follow the approach that best fits your business needs.
If you wish to change it, please refer to the below mentioned article/video to change the Prefix:
Article -
Video -
Please refer to the below mentioned article to change the Suffix:
Article -
https://community.getswipe.in/t/how-to-add-suffix-for-current-financial-year-25-26-in-android/2114