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  35  Payment of the balance may take the form of recovery. Payment of the invoice and approval of documents does not imply recognition of the regularity,  authenticity, completeness and correctness of the declarations and information they contain. 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.6, in  the tender specifications or in the specific contract. The contractor (or leader in the case of a joint tender) must send an invoice for interim payment, as  provided for in Article I.6 or in the tender specifications or in the specific contract. The contracting authority must not request a retention money guarantee for a specific contract where  it has requested a performance guarantee. Retention money guarantees cover full delivery of the service in accordance with the specific 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 specific contract. The  contracting authority must release the guarantee after the expiry of the contract liability period as  provided for in the specific 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 specific contract. The contracting authority must release the  guarantee fully after final approval of the service, as provided for in the specific 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:  (a) the contracting authority bears the costs of dispatch charged by its bank;  (b) the contractor bears the costs of receipt charged by its bank;  (c) the party causing repetition of the transfer bears the costs for repeated transfer.  (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). 