Tax code S2 may only contain one assignment line-Input Service tax

There is one interim service tax input code (for normal services) - S1. Final service tax code S2 is created assigned to S1 as target tax code.

Entry passed:

Exp A/c.. Dr 500000

Service Tax Basic (deferred) 50000

Service Tax ECS (deferred) 1000

Service Tax SHEC (deferred) 500

To Vendor A/c 551500

But when i execute the program i can see three line items (for basic, interim and SHEC)

But when i run the session, it gives error:

Tax code S2 may only contain one assignment line.

I AM UNABLE TO UNDERSTAND, WHY ITS GIVING ERROR FOR Input SERVICE TAX TRANSFER

But for output Service tax Interim-I1 and final Service tax code-T1- means in case of customer, the deffered tax transfer cycle is working fine.......

regards