Package format
An AppImage is convenient when you want a portable build across many Linux distributions. A DEB package is useful on Ubuntu or Debian-based systems where package installation is preferred.
PDF invoice export
The app should generate clean PDF invoices that are easy to send, print, and archive. Test at least one real invoice before committing your workflow.

Backup and restore
Offline invoice software gives you control, but you must protect the database. Choose software that makes backup and restore easy to understand.

Tax and currency fields
If you bill Indian customers, check for GSTIN, HSN, and tax rate fields. If you work internationally, check currency and invoice template flexibility.
Invoiso provides Linux builds and offline PDF billing. See the invoice software for Linux page or download Invoiso.
