1. Open your iPhone and click to enter the AppStore.

2. Search for "invoice" or "electronic invoice" in the AppStore to find the appropriate invoicing software.

3. Click to download and install the invoicing software.

4. After the installation is completed, open the software and follow the prompts to register and log in.

5. Fill in the corresponding information and save the invoice according to the template provided by the software.

6. When needed, the invoice can be exported or printed, or the invoice can be stored in the cloud for viewing at any time.