Input credit of service tax

good evening all, dear experts the whole senerio is that I am working in a co. which engaged in business of clearing and forwarding of shipments. now I got an invoice DT 5th april from shipping line which is inclusive of service tax. but the job against which I got that invoice had been completed in march and we have been raised invoice to our customer in march ag.said job. now my query is that can we book this invoice DT. 5th April in march because income against said exp already booked in march and also can we take input credit of service tax in March as well. the thing to keep in mind is that exp. invoice I got against said job is of dtd. 5th April. please show me light in this regard. thank you all in advance.