If the reply link doesn't appear, click the timestamp, and it'll be there. :)

As for french invoices, i use this phrasing:

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You gave this contract using your VAT-IdNr.: * As per "Art. 196 MwStSystRL" the tax liability is transferred to you as service recipient (reverse charge process / TVA due par le client).

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Since i invoke the same § for the UK invoices, i suspect that it's a germany-specific thing.

Notable is also, that, as others mentioned, i don't deal with non-business customers.

Also yes, i did sign a contract with him that specifically assigned liability as long as i follow his instructions and provide accurate information.