Dear Sir,
In reference to your query, RCM is payable under 2 procedures.
1. Where the vendor is registered but supply is under RCM. - In that case your liability would arise on the date of vendor invoice date.
2. Where the vendor is unregistered and supply is under RCM - In this scenario, the govt. has allowed clubbing of all the invoices of that vendor in a period into one single self-invoice which you need to raised on yourself.
In this case, your liability would arise on the date of self-invoice.
Hope I have been able to address your query.
Please advise in case of any further clarification.
Thanks & Regards,
CA Aditya Dhanuka.