If you hire an outfitter, s/he will expect you to pay the entire amount in advance. In such case, you can pay by direct bank transfer, check, and / or credit card. So, you can do with less cash.
But if you prefer to aggregate all travel services on your own, you should have cash handy. Because the camping staff, including porters expect immediate payment in cash. They do not accept plastic money and / or checks. The shops in small and big villages along the trail do not accept plastic money either.
You should carry enough cash safely as automatic teller machines (ATMs) are either rare sight or do not exist beyond Nauti. The starting point of the jat Nauti has one ATM managed by State Bank of India (SBI).
Both Punjab National Bank and Union Bank of India offer ATM services in Karanprayag, less than an hour’s drive from Nauti.
The trail does not feature any foreign exchange agents. So, carry enough amount of Indian currency.