Mortgage loan to buy a house, mortgage loan procedures can be invoiced. After the bank mortgage loan is successfully handled, you can go to the developer for a unified invoice for real estate sales. The payer issues an invoice to the payee. When buying an auction house, property buyers must ensure that developers have the following five certificates: state-owned land use permit, construction land planning permit, construction project planning permit, construction project construction permit and commercial housing sales (pre-sale) permit, all of which are indispensable.