It is illegal for a friend to take the client's invoice to reimburse him.
 No unit or individual may lend, transfer or introduce others to transfer invoices. Invoices refer to the business vouchers issued and collected by all units and individuals in the purchase and sale of goods, provision or receipt of services, and other business activities. They are the original basis for accounting and an important basis for the audit and tax authorities to carry out law enforcement inspections. The receipt is the receipt and payment voucher. The invoice can only prove that the business has occurred, not whether the payment is received or not.
 How long is the validity period of invoice reimbursement?
 The reimbursement period for invoices is half a year.
 1. The reimbursement of invoices should be made in the month when the invoice is issued or the more timely the better, but it should not cross years.
 2. The invoices used for reimbursement by the company must be recorded in the current month to determine the revenue, and the validity of the special VAT invoices obtained is 180 days.
 3. The units and individuals that draw up invoices shall store and keep them in accordance with the provisions of the tax authorities, and shall not damage or destroy them without authorization.
 4. The counterfoil and invoice register already issued shall be kept for 5 years. To sum up, it is illegal for a friend to take my invoice for reimbursement. No unit or individual is allowed to lend or transfer the invoice. Are you clear? Article 24 of the Measures of the People's Republic of China for Invoice Management Any unit or individual shall use invoices in accordance with the regulations on invoice management and shall not commit any of the following acts:
 （1） Lend, transfer or introduce others to transfer invoices, invoice supervision seal and special products for anti forged invoices;
 （2） Know or should know that invoices are privately printed, forged, altered, illegally obtained or invalidated, and are transferred, drawn up, stored, carried, mailed or transported;
 （3） Use invoices in separate copies;
 （4） Expand the scope of invoice use;
 （5） Use other vouchers instead of invoices.
 The tax authorities shall provide convenient channels for inquiring about the authenticity of invoices.