However for the older churches they may have had a graveyard in the past, burials ceased and the graveyard has been re-used. This is most likely in towns and cities where the value of the land has influenced this. A good example is St John's, Blackpool which visually appears not to have one, but it did and Church Street in front of the church runs through the graveyard. My grandfather was a platelayer on the trams, and it was 'urban legend' among the gang that if you worked on the track there you could dig up gold rings!
The event that had most influence over this was the passing of a law in the mid 1850s prohibiting burials within towns and cities due to public health reasons. With the large populations, there were more burails than the ground could accommodate. So if the church was founded in a twon after 1860 and there is no graveyard now, then it is a reasonable assumption that there has never been one. Of course you need to work from the original founding date, not that of a particular building.
For the older churches further research is required. Maps sometimes show graveyards, and of course if there are burial registers that is another big clue. However just because a funeral service may have taken place at the church it could have been for a burial that took place elsewhere. Similarly the church may hold a burial register for a graveyrd they own which is actually out of town.