Canceling a Trip that has been Posted 
In Travel Management, you can cancel trips that have been posted in Accounting.
Integration
To make the cancelation, you have to change the trip status to settlement status Canceled. You can do this by using the entry scenarios or the Approval Program. In the approval program, the trips and requests are given the settlement status Po. Can. (posting canceled) and the status Corr. (corrected).
The next settlement run also includes trips that have the settlement status Canceled. The settlement program replaces the old payroll period of these trips with the payroll period you used to start the settlement program.
The next time settlement results are transferred to Accounting after the settlement run, the system includes the trips that have settlement status Canceled in the posting run. Cancelation of postings in Accounting occurs when you post the posting run.
In the approval program, finally, the trips and requests are given the settlement status Can.po. (cancelation posted).
Negative Postings
If you have permitted negative postings in Financial Accounting, these are also valid when you reverse travel expenses. In this case a debit posting reduces the credit side of the account and a credit posting reduces the debit side of the account.
In Customizing for Financial Accounting, you activate negative postings under 
Financial Accounting Global Settings 
Global Parameters for Company Code Enter Global Parameters 
, by selecting the Negative Postings Allowed checkbox. Since travel expenses cannot contain both positive and negative document items, you do not need to define document types that allow individual identification of document items as negative postings.
Activities
If you want to cancel a trip, change the Trip Assignment Status to Canceled.