Service tax on payments wrongly credited

Hello Experts,

I have 2 sister concern companies which were de-merged on 01.04.2012.

Now one of our clients has wrongly deposited the amount due on a bill in the account of our sister concern.

Will there be any service tax implication if i merely transfer the amount to our sister concern rather tham refunding it back to the party and then my sister concern claiming it back from the builder???

I personally feel that there shouldnt be any issue... however, my sister concern accountant stresses that there would be...

Request your help

Regards,

Anitha Serrao