Cache and cash are easily confused words. They are homophones, meaning they sound identical, but are spelled differently and mean different things.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Cache is noun. It means a small storage space in the ground, or a small bundle of hidden goods. It can also mean temporary storage on a computer.
Cash is a noun. It means paper currency or money.
The following story uses both words correctly:
Caspian was having computer problems. The screen kept saying caches were out of memory. He aimed to fix it himself, because he didn’t have the spare cash to consult someone else.