Wells Fargo & Co. has fired or suspended more than a dozen employees in its investment bank and is investigating dozens of others over alleged violations of the company’s expense policy regarding after-hours meals, according to people familiar with the matter.

At issue is whether Wells Fargo WFC, +1.37% employees ranging from analysts to managing directors in New York, San Francisco and Charlotte, N.C., doctored receipts on dinners that they charged to the bank, the people said.