SAP is interfaced with numerous systems by numerous businesses. Some businesses have historically posted AP and AR transactions from non-SAP systems into the SAP system. You may construct the FI AR-AP interface to upload documents from Non-SAP systems with the help of this blog post. You will gain knowledge of the crucial considerations that must be made when creating the interface application that posts documents into SAP from non-SAP systems.

Field Choice:

For each interface, field mapping with a legacy system (a non-SAP system) is necessary in order to submit the document in SAP. A few fields, including the Posting date and Document date, Document type, Amount, GL account, Customer or Vendor, etc., are required in order to publish the AR and AP documents. Additionally, you must determine the fields that the company needs for its procedures, such as reference, assignment, and text, etc. As a result, integrate a non-SAP system with all of the SAP fields. Think about and give the legacy system the correct field information, such as the field’s length, decimal places, and data type (date, char, numbers, etc.).

Changing Rate:

When we create an interface in SAP to upload the documents, the exchange rate is crucial. To avoid any inconsistencies and to maintain the integrity of your financial accounts in both systems, the amount in local currency should always equal in both.

  • Since users can manually enter the conversion rate when uploading documents on most systems, it is always preferable to obtain the exchange rate from a non-SAP system because it corresponds to the real currency rate in the document.
  • You can obtain the amount in transaction currency and local currency from the non-SAP system if you do not want to use the conversion rate from that system. This way, there won’t be any chance of inconsistencies between the two systems, and the data will be in sync.
  • In both systems, a disparity in local currency amounts might result from a single decimal place difference. Make sure that the exchange rate has the same decimal places in SAP and your legacy system.

Always avoid computing tax amounts in SAP when uploading documents for AP and AR. The tax amount may vary across the two systems if the legacy system’s tax amounts are manually changed. Rounding regulations in both systems can also cause disparities in tax amounts. As a result, the actual invoice copy and SAP reports will reflect inaccurate tax reporting. In order to map the tax code, tax amount, and tax base amount to SAP fields, you should obtain them from legacy systems.

Verify that all of your custom and regular tax reports contain the correct tax base amounts, tax amounts, and tax codes for all documents that were uploaded using the interface.

Customers and suppliers:

For documents to post from the non-SAP system, you must obtain the vendor and customer. Based on your architecture of customers’ and suppliers’ master data with a non-SAP system, you can have a separate interface for master data or map the customer and vendor numbers to legacy systems.

The GL Accounts

Determining the GL account depends on the legacy system and operational procedures. If the chart of accounts for the non-SAP system and SAP system are mapped, then SAP will receive GL accounts from the non-SAP system directly. If there is no chart of accounts mapping between the two systems, then you must create GL account determination tables in SAP or Legacy system based on business requirements, such as the VKOA table in SAP.

Associated Fields:

Some fields in AR and AP documents depend on business processes in order to be identified and filled out with the appropriate data. Here are a few instances:

  • Tax reports must include the customer invoice number, thus if a legacy system generates the number, it must be kept in the appropriate field as a reference and utilised in SAP standard tax reports. Check your customised reports as well, particularly those that use the client invoice number.
  • In order to clear incoming payments or any other manual or automatic clearing, map the assignment field with the appropriate field and fill it with the appropriate data.
  • Check what fields appear on statements for the invoice number and make sure this field data is entering SAP from the interface. Your Customer statements or periodic statements that SAP delivers to customers or vendors should have the invoice number.
  • Determine any additional fields that are necessary for the operation of the business, taking your customised reports and transaction codes into account.
Managing Data:

Examine the requirements for data control in your business processes, such as profit centres, cost centres, COPAs, etc. Create a table based on the business requirements to identify the cost and profit centre if the legacy system is not supplying the controlling data. Make sure that all CO documentation are produced in accordance with business procedures and that all control reports are accurate.

Fields for Customs

A small amount of field data from older systems may need to be stored in SAP documents for business needs. Create custom fields in table ACODCA (in S4 HANA) or BSEG to map this data. You can also use standard fields like reference key 1, 2, and 3 that aren’t used in your publications.

Types of documents

It is preferable to establish new document types since they are always simple to identify from the interface and can be traced quickly if there are any problems. Depending on the business requirements, construct new document types or utilise the same standard document types as KR, KG, and DR, DG. Additionally, by using a filter based on document types or creating a custom report, any reports the company might require in the future can be quickly extracted.

Change of Direction:

You must take into account how to reverse the document in the legacy system. You must manually clear the reversed document in SAP with the original document if you reverse the document in a non-SAP system and then post the reversed document in SAP through the interface. Alternatively, you can schedule a job to automatically clear reversed documents in SAP.


There are numerous fields that must be considered while creating a new interface. When building the interface, always double-check the necessary fields, the business needs, and the dependent fields. To comprehend each field, you need also be familiar with the Non-SAP system’s FI document posting procedure.