The alcohol was being sold without duty being paid, amounting to over £20,000, HMRC said, though no arrests have yet been made.
HMRC described investigations as "ongoing pending potential prosecution".
The seizures included 8,352 bottle of beer and cider, 371 bottles of wine and 10 bottles of spirits from an off-licence in Sedgley, Birmingham.
Almost 3,800 cans of beer, 812 bottles of wine and 62 bottles of spirits were seized from an off-licence in Birmingham's Boldmere district.
A raid on a wholesaler in Rowley Regis tralwed 2,760 cans of beer and 676 bottles of spirits.
HMRC spokeswoman Jennie Kendall said: "This illegal trade has a devastating effect on legitimate retailers having to compete with black market traders, particularly at Christmas, one of the busiest times of the year for alcohol sales."