In App Manage Automatic Payments in View Log Item is blocked with block key A is shown.
In Exceptions Tab Error ID (Description): 003 (Item is blocked for payment)
Down payment is Blocked for payment

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SAP S/4 HANA Cloud 

1. In SSCUI  Set Up All Company Codes for Payment Transactions  101293
   Example in Section
   Vendors
   Sp. G/L transactions to be paid  AF
   (Special G/L Indicator A= Downpayment
   Special G/L Indicator F= Down Payment Requests)
2. In App Manage Supplier Down Payment Requests (app ID F1688) create down payment request.
3. Post Down payment in app Manage automatic payments  (app ID F0770)
4. Create Supplier invoice in app Create Supplier invoice (app ID F0859)
5. In app Manage Automatic Payments enter Down Payment and Supplier Invoice 

• The payment program always sets the payment block 'A', when creating down payments using down payment requests when in customizing Set Up All Company Codes for Payment Transactions Special G/L Indicator A= Downpayment is included in addition to F. 
  
  
• The system will not automatically clear down payments in the next payment run.

If the special G/L indicator for down payments example A is not entered as a special G/L indicator that is to be paid in Customizing Set Up All Company Codes for Payment Transactions, the payment program usually does not take the down payments into account, only the supplier Invoice. In this case in customizing Set Up All Company Codes for Payment Transactions Sp. G/L transactions to be paid is F only for Vendor/Supplier 

In this case, the payment block is not required.  The setting of the payment block is therefore adjusted to the program logic for manual posting

See Test Script Accounts Payable (‏J60‏)  and Accounts Receivable (‏J59‏)  for steps on down Payments process including  

Clear open items. 

Down Payments

Manage Supplier Down Payment Requests

KBA , FI-FIO-AP-PAY-2CL , Payment Apps (Public Cloud) , FI-FIO-AR , Fiori UI for Accounts Receivable , FI-FIO-AP-2CL , Fiori UI for Accounts Payable (Public Cloud) , FI-FIO-AP-PAY , Payment Apps , How To

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