Can proprietor dealing with Export of Service + Tax Audit use Cash Based Accounting Instead of Accrual Based?

Income Tax 1961 Tax Audit
1

Use-Case: A proprietor dealing 100% with export of service and goes through Tax Audit every year.

Can he use Cash-based accounting or he has to use accrual based only?

Cash based accounting is more better for his use-case. He CA has been using Accrual based but proprietor wanted to switch.