台Taivo A Taiwan Mandarin dictionary

陰陽合同

yīnyánghétóng

ㄧㄣㄧㄤˊ ㄏㄜˊ ㄊㄨㄥˊ

Simplified 阴阳合同

1a deal where the parties collude to sign an under-the-table "yin contract" 陰合同|阴合同 as well as an ostensibly genuine "yang contract" 陽合同|阳合同 in order to deceive authorities

Keep 陰陽合同 and it comes back until you know it.