Is the supplier required to observe any established contract form when concluding the electricity supply contract with the applicant?

The supplier must conclude electricity supply contracts with domestic or non-domestic consumers in strict compliance with the mandatory clauses of the electricity supply contract, specified in Annexes 2 and 3 of the Regulation on electricity supply, published in OG no. 59-62/308 of 4/15/2011. The supplier is neither entitled to change the mandatory clauses of the contract nor add unilaterally other provisions to it. Any addition to the contract, for both domestic and non-domestic consumers, shall be valid only if made in writing and signed by the both parties, being a separate appendix to the contract.