Hi, not sure if you've resolved this, but in case others are looking for an answer....

Roughly per the documentation at present : https://www.odoo.com/documentation/user/11.0/accounting/others/taxes/cash_basis_taxes.html

Accounting ‣ Configuration ‣ Settings ‣ to tick the Cash Basis option and select the Cash Basis Journal which appears to pre-select your currency. (Or at least mine is appropriately showing my currency based on our country based set up).

I had to check GL account set up at this point and create/give the GL codes names relevant to my country set. I now have:

GST To Collect (Current Liability) – accrual record from AR invoices

GST To Pay (Current Assets) – accrual record from AP record

GST (Cash Basis) (Current Liability) – cash movements converted from the accrual records upon reconciliation of the bank transaction

GST is a VAT type tax

Accounting ‣ Configuration ‣ Taxes to go to the individual tax rates. On the front page use the appropriate AP or AR based code. For simplicity I have selected the one account for both options here. On the Advanced Options tab, at the end, select Tax Due - Based on Payment, which will bring up a selector for choosing your GST (Cash Basis) equivalent for all cases.

Use the documentation as a guide, as even though it looks like it was written for an earlier version, the accounting treatment should be the same and it gives an example of an appropriate account to use for the example sales tax they have there. 

I can replicate their example with the above set up (on backup/dev database) and will keep an eye on it in our primary/prod database for the first couple of types of AR and AP transactions.

Just a disclaimer, I am not a qualified accountant and am trusting my own accountant won’t be too frustrated with this setup. While not a typical treatment in my country, assuming I haven’t missed anything, it does balance in the end.

Now in V11,

• First you have to activate "Cash Basis" from accounting setting.

• Once you enabled, on the tax form you can find two options(in advance options tab),

•  Tax Due : 1) Based on Invoice 2) Based on Payment