Formal Chinese numbers

Something my dad explained to me when I was a kid that I still remember. I first saw the "complicated" Chinese character for one on currency: 壹. I asked my dad why didn't they just write: 一? He said, it's to forestall forgery or alteration, just as one spells out an amount in words on cheques in English. Being an accountant, he knew all that.

Here are the formal numbers from 0 to 10 in Chinese:  零壹贰叁肆伍陆柒捌玖拾. Pronunciation is identical. Here's the blog post I found which gives more details.

Right, that's 壹萬 bucks you owe me