The announcement is part of the bank's latest round of job cuts, which will see 420 posts lost across the UK, mostly in wholesale banking and insurance.
In addition to the 50 Black Horse jobs, which are based in Orchard Brae, another 20 posts will be lost in Scotland, mostly in Glasgow.
A spokesman said there had been reduced demand for Black Horse personal finance products, but said customers would not be affected.
He stressed the Black Horse motor finance division, also based at Orchard Brae, was not involved in the job losses.
The posts will go in June or July next year.
The spokesman said: "Between now and then we will try to find people jobs elsewhere in the business."