African Union Legal Instrument P a g e | 11 b. However, the natural or legal person may be released from all or part of the liability by proving that the non-fulfilment or poor performance of the contract is due either to the contractual partner or a case of force majeure. Article 6: Writing in electronic form 1. Without prejudice to existing domestic legislative provisions in the State Party, no person shall be compelled to take legal action by electronic means. 2. a. Where a written document shall be required for the validity of a legal act each State Party shall establish the legal conditions for functional equivalence between electronic communications and paper-based documents, when the internal regulations require a written document for the validity of a legal act. b. Where a paper document has been subject to specific conditions as to legibility or presentation, the written document in electronic form shall be subject to the same conditions. c. The requirement to transmit several copies of a written document shall be deemed to have been met in electronic form, where the said written document can be reproduced in material form by the addressee. 3. The provisions of Article 6.2 of this Convention do not apply to the following: a) Signed private deeds relating to family law and law of succession; and b) Acts under private signature relating to personal or real guarantees in accordance with domestic legislations, whether made under civil or commercial law, unless they are entered into by a person for the purposes of his/her profession. 4. The delivery of a written document in electronic form shall be effective when the addressee takes due note and acknowledges receipt thereof. 5. Given their tax functions, invoices must be in writing to ensure the readability, integrity and sustainability of the content. The authenticity of the origin must also be guaranteed. Among the methods that may be implemented to fulfil the tax purposes of the invoice and to ensure that its functions have been met is the establishment of management controls which create a reliable audit trail between an invoice and a supply of goods or services.