Contract number: [ complete ]  Service contract conditions of December 2018  II.21.4. Costs of transfer  II.21.5. Pre-financing, performance and money retention guarantees  II.21.6. Interim payments and payment of the balance  34  The contractor (or leader in the case of a joint tender) must send an invoice for payment of the  balance within 60 days of the end of the period of provision of the services, as provided for in  Article I.5 or in the tender specifications. The contractor (or leader in the case of a joint tender) must send an invoice for interim  payment, as provided for in Article I.5 or in the tender specifications. The contracting authority must not request a retention money guarantee where it has  requested a performance guarantee. Retention money guarantees cover full delivery of the service in accordance with the contract  including during the contract liability period and until its final approval by the contracting  authority. The retention money guarantee must not exceed 10 % of the total price of the  contract. The contracting authority must release the guarantee after the expiry of the contract  liability period as provided for in the contract.  Performance guarantees cover compliance with substantial contractual obligations until the  contracting authority has given its final approval for the service. The performance guarantee  must not exceed 10 % of the total price of the contract. The contracting authority must release  the guarantee fully after final approval of the service, as provided for in the contract. Pre-financing guarantees must remain in force until the pre-financing is cleared against  interim payments or payment of the balance. Where the payment of the balance takes the form  of a debit note, the pre-financing guarantee must remain in force for three months after the  debit note is sent to the contractor. The contracting authority must release the guarantee  within the following month. The contractor bears the cost of providing such guarantee.  If, as provided for in Article I.6 , a financial guarantee is required for the payment of pre- financing, as performance guarantee or as retention money guarantee, it must fulfil the  following conditions: The costs of the transfer are borne as follows:  (c) the party causing repetition of the transfer bears the costs for repeated transfer.  (b) the contractor bears the costs of receipt charged by its bank;  (a) the contracting authority bears the costs of dispatch charged by its bank;  (a) the financial guarantee is provided by a bank or a financial institution approved by the  contracting authority or, at the request of the contractor and with the agreement of the  contracting authority, by a third party; and  (b) the guarantee shall have the effect of making the bank or financial institution or the  third party provide irrevocable collateral security, or stand as first-call guarantor of the  contractor's obligations without requiring that the contracting authority has recourse  against the principal debtor (the contractor). 