Answer:

lineone

Answer	Crossword Clue
LINEONE	Office phone button, maybe
LINEONE	Start of a typewritten page.
LINEONE	What the first caller may be on

LINEONE	Phone system starting point
LINEONE	Start of a form to fill out
LINEONE	What a priority call arrives on
LINEONE	Office phone button
LINEONE	Start of a bureaucratic form
LINEONE	Spot for gross receipts or sales on Schedule C