Customize Invoice Templates with AI

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Feature idea: Users can generate their own custom invoice templates through prompting an LLM.

After the LLM connector is active, the user could describe their desired design as a prompt. The system prompt refers to existing templates and ensures that the template is valid.

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Tester Review: Refinements

Two additions from tester feedback:

1. Enforce section 14 UStG mandatory fields

The system prompt must ensure the LLM never omits legally required invoice fields:

• Tax number or VAT ID
• Service period (start/end date)
• Sequential invoice number
• VAT amount disclosure (rate + amount per line)

The user may freely customize layout, colors, and typography, but these fields must always be present in the generated template.

2. Iterative preview loop

Add a design iteration workflow:

1. User describes desired design in natural language
2. LLM generates an HTML/CSS template
3. Tuttle renders a preview with sample data
4. User gives feedback
5. Repeat until satisfied

This makes template customization tangible and low-risk -- the user sees exactly what they get before committing.