We file every year but never talk to our accountant until the deadline is close
Most contractors we meet have a preparer who assembles a return once a year and nothing else. There is no call in September about whether the owner's salary from the S corp still makes sense, no heads up before a new service van is bought in December, and no warning that a strong summer blew through the quarterly estimate. By the time the return shows up in March, the truck is already paid for and the tax bill is already locked in.
This happens because most firms staff up for filing season and have nobody left over to plan during the year. The owner assumes no news means everything is fine, when nobody has actually looked closely enough to know one way or the other.
Left alone, this costs real money every year: an S corp salary set too low draws IRS attention and can be reclassified with back payroll taxes, penalties, and interest; a quarterly estimate that falls short after a busy summer adds an IRS underpayment penalty on top of the tax itself; and a December equipment purchase timed wrong can push a deduction into the wrong tax year and cost thousands in cash you didn't need to spend that April.