If it is to confirm the real estate, of course, you must bring the real estate license.
I suggest you notarize an agreement, that is, your sister writes an agreement on the transfer of real estate, and then notarize this agreement.
But it seems that this also requires a real estate license. This is the address and telephone number of some notary offices in Beijing. You can call them for advice first.
Beijing Fiona Fang Notary Office 65538988 Beijing Inn Building, No.5 Dongshuijing Hutong, Dongcheng District, Beijing
Beijing Fangzheng Notary Office 68096 188 4th Floor, SDIC Building, No.7 Fuwai Street, Xicheng District, Beijing
Room 7 15, Capital Building, No.6 Chaoyangmen North Street, Dongcheng District, Beijing, 6554478, Beijing Chang 'an Notary Office
Beijing Oriental Notary Office 842 17035 Floor 1, Conference Center, Haiyuncang Hutong 1, Dongcheng District, Beijing
Beijing National Notary Office 66 183570, No.68 Deshengmen West Street, Xicheng District, Beijing
Beijing CITIC Notary Office 5260 1 155 Xicheng District, No.2 Guangningbo Street, Xicheng District, Beijing
Beijing Xinde Notary Office 67 124408 Floor 4, Building 3, zhushikou East Street, Chongwen District, Beijing
Beijing Jingcheng Notary Office 63580038 No.24 Caiyuan Street, Xuanwu District, Beijing
Beijing Zhengyang Notary Office 8596 1236 No.23 Shuiduizi East Road, Chaoyang District, Beijing