Usage patterns
〈事〉が赤字になるfor something to go into the red / run a deficit
This year's financial results went into the red.
赤字で書くto write in red ink
Please write the important parts in red.
赤字を入れるto mark corrections in red ink
The teacher made corrections on the manuscript in red ink.
赤字を出すto post/incur a deficit
That company has posted a deficit for three years in a row.
赤字を抱えるto be saddled with a deficit
Many local governments are burdened with deficits.
赤字を解消するto eliminate/clear a deficit
They eliminated the deficit through cost cutting.
Expressions
赤字覚悟prepared for a loss; ready to operate at a deficit