reserve fund; accumulated fund
A fund built up by setting aside money regularly, often for a specific future purpose. Compare 準備資金, which is a more general term for reserve funds.
See also: 準備資金
I'm gradually increasing my reserve fund every month for retirement.
The company secured a reserve fund for equipment renewal.
準備資金 is a broader term for any reserve or preparatory fund, while 積立資金 emphasizes the process of accumulating the fund over time through regular contributions.
Standard kanji spelling.
Spelling with okurigana; slightly more explicit reading.
Compound of 積立 (つみたて, 'accumulation, setting aside') + 資金 (しきん, 'fund, capital').