What sin does a Catholic commit who neglects to receive Holy Communion worthily during the Easter time? A Catholic who neglects to receive Holy Communion worthily during the Easter time commits a mortal sin.
He who eats my flesh and drinks my blood has life everlasting and I will raise him up on the last day. For my flesh is food indeed, and my blood is drink indeed. (John 6:55-56)
What is the Easter time in the United States? The Easter time in the United States begins on the first Sunday of Lent and ends on Trinity Sunday.
More on that -> CCC 1384-1390