According to IRAS Audit File sample transaction entries, if there's any purchase of items are classified as Customer Accounting from supplier, reverse charge mechanism posting would be done.

Eg: Purchase from Peng Peng B.V. with 500 Mobile Phones with Tax Code TXCA (Tax rate 7%), according to Customer Accounting logic, system need auto reverse an entry with Tax Code SRCA-C (Tax rate 7%)

It's mean that whenever your supplier issue a Customer Tax Invoice to you with supply of Tax Code SRCA-S (Tax rate N/A with 0%), you shall input such purchase with TXCA (Shouldn't claim 7% since SRCA-S N/A of tax rate), However with acknowledge to IRAS, it need REVERSED the taxable amount with SRCA-C on Supply Section.