Invalid while client try to issue invoice for him self

i tried to issue invoice for my self because i have multi property so sometime i become a seller and buyer on same time because all my properties on same vat registeration number so do i need to issue any thired party or self invoive for my self . or i donot need to issue any one of them.

An Error Detected during Validation !

[BR-CUSTOM-VALIDATION-01]- The Seller VAT registration number or seller group VAT registration number (BT-31) of The invoice must not match the buyer VAT registration number (BT-48).