账 (zhàng, accounts) and
帐 (zhàng, tent / curtain) used to be interchangeable for the 'accounts' meaning, but modern standard usage strictly separates them: financial 'accounts' is always
账, while
帐 is reserved for
帐篷 'tent' and
蚊帐 'mosquito net.' CC-CEDICT lists
记账 as the modern form and
记帐 as the older variant.