In Japan, many companies close their books in March, so March is especially busy.
Many companies in Japan end their fiscal year in March, so that time of year is really busy.
決算 = closing accounts, settling accounts, closing the books, 専門用語で "the close"
fiscal year = 営業年度
例：
In Japan, many companies close their books in March, so March is especially busy.
日本では３月決算の企業が多いので、3月は繁忙期です。
Many companies in Japan end their fiscal year in March, so that time of year is really busy.
日本では３月に営業年度が終わる企業が多いので、3月は繁忙期です。
For many companies in Japan, March is the end of the tax/accounting/fiscal year so everyone is very busy.
It's difficult for us to take days off work in March because it's the busiest period of the year.
「日本では３月決算の企業が多いので、3月は繁忙期です。」＝ For many companies in Japan, March is the end of the tax/accounting/fiscal year so everyone is very busy.
It's difficult for us to take days off work in March because it's the busiest period of the year.
(3月は繁忙期なので休みを取りにくい。）
ボキャブラリー
many companies ＝ 多くの会社
in Japan ＝ 日本に
March ＝ 3月
end of the tax/accounting/fiscal year ＝ 月決算
so ＝ だから
everyone ＝ みんな
very busy ＝ とても忙しい
take days off work ＝ 仕事の休みを取る
busiest period ＝ 一番忙しい時期
アメリカ合衆国 
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