Substitution in Accounting Document

I have configured the automatic payment processing. But I am faced with a problem in that I want the cheque number that is created, in the assignment (allocation) field of the payment document so that I can use it in Bank Reco and clearing.

I think I can used Substitution rules.

Substitution rules can be written for any fi doc getting created.
The Creation of rules are very user friendly.
In IMG path is financial accounting global setting - documents - line items - define substitutions

OSS notes Substitutions/Validations 42615 and 100261 and 20637 are helpful.

Sap Help documentation is available. But substitution is fairly easy. Just go as per the steps and you will get it.

I do not know how you are going to get the check number from. I tried to see whether it is available in any table but couldn't find it.

RFCHKU00
This is a readymade program available from 4.0c onwards to copy
check number in assignment /ref. field.