"Heaven's Just a Sin Away" is a song composed by Jerry Gillespie, which was recorded in 1977 by The Kendalls. Released in 1977, the song went to Number One on the Billboard Hot Country Singles (now Hot Country Songs) charts. It was the duo's first Top 40 entry on that chart, and the second single from the album Let the Music Play / Heaven's Just a Sin Away, released on Ovation. It also reached number 69 on the Billboard Hot 100.

Answer this question: who sang heaven is just a sin away? Let's give stream of consciousness first:
The important part for answering this question is: "Heaven's Just a Sin Away" is a song composed by Jerry Gillespie, which was recorded in 1977 by The Kendalls.
So, the final answer is The Kendalls.