noun
Primarily used in financial and accounting contexts to refer to excess funds or a remaining balance after expenses.
決算の結果、剰余金が生じた。
As a result of the settlement of accounts, a surplus was generated.
剰余金は翌年度
The surplus is carried over to the next fiscal year.
黒字 means 'in the black' or a profit, while 剰余金 refers specifically to the surplus amount itself.
Compound of 剰余 (surplus, excess) and 金 (money). The exact historical derivation is uncertain, but the word is a straightforward Sino-Japanese financial term.