Business Rules for Electronic Invoicing
Electronic invoicing is Ameren’s preferred method of doing business with its vendors. The following are the business rules you must follow to be part of our electronic invoicing program.
1.	Ameren Purchase Order Must Be Issued
	In most cases, do not accept an order without a purchase order number. You can only send an electronic invoice for materials or services ordered with a purchase order. In addition, your electronic invoice must contain a nine digit PO number. You must submit a paper invoice to Ameren’s Accounts Payable Department if a purchase order was not issued to you.
2.	You Must Receive an Electronic PO to Invoice Electronically
	Hosted Order Management (HOM) vendors: If a PO is sent to you outside of HOM (fax, email, or US mail), you cannot invoice the PO from HOM. Paper copies of invoices should be sent to the Ameren Accounts Payable Department for processing. It should only be necessary for you to receive a PO outside of HOM when attachments are required.    Integrated vendors: If you receive a PO by a means that requires you to manually enter it in your order management system, it is recommended that you do not attempt to invoice electronically. This usually means you received a PO via fax, email, or US mail. It should only be necessary for you to receive a PO this way when there are attachments that cannot be sent electronically. Paper copies of these invoices should be sent to the Ameren Accounts Payable Department for processing.
3.	Prices Cannot Exceed Three Decimal Places
	All line item, tax, freight, and miscellaneous charges can not be more than three decimal places.
4.	Quantities Cannot Exceed Two Decimal Places
	Quantities invoiced for each PO line item can not be more than two decimal places.
5.	A Subcontractor Cannot Invoice Ameren Directly
	If it is necessary for you to have another company fill an Ameren purchase order, the electronic invoice must still be submitted by your company; not the company who filled the order.
6.	Standalone Charges Cannot be Invoiced Separately
	Miscellaneous charges such as taxes and freight must be billed on the same invoice as the applicable materials or services.
7.	Description of Miscellaneous Charges Must Be Provided
	Ameren’s electronic invoicing process allows you to bill miscellaneous charges as necessary. A description of these charges must be included as part of the electronic invoice.
8.	Invoice Numbers Larger than 10 Characters
	Ameren’s accounts payable system cannot accommodate more than 10 characters in the invoice number field. If your invoice number exceeds 10 characters, you must make your Ameren electronic procurement representative aware of this before implementation.
9.	Unit-of-Measure Must Match Ameren’s Purchase Order
	Your company is required to invoice in the same unit-of-measure in which Ameren orders materials or services. In addition, the unit-of-measure code must be identical (FOT for foot; not FT).
10.	Orders Paid by Credit Card
	If you receive a purchase order for materials or services paid by credit card, do not send any XML documents to Ameren (PO acknowledgement, credit card acknowledgement, invoice, etc.).
11.	Paper Invoices
	A paper invoice should not be mailed for any invoice that has been or will be sent electronically.
12.	Customary Terms and Conditions
	All customary Ameren terms and conditions apply to each electronic procurement transaction. Contact Ameren’s Purchasing Department to obtain a copy of our terms and conditions.