I helped you with a couple bugs. Variables m and l needed to be integers. Variable r was clarified to be % anually. The output function needed to use the variable t for each month to calculate properly.

def info():
  i = float(input("initial investment: "))
  r = float(input("intrest rate % annually: "))/100
  m = int(input("how long are you investing in months?: "))
  l = int(input("how long has your investment been going? "))
  return(i, r, m, l)

def calculate(i, r, m, l):
  d = i*(1 + (r/12)*m)**(l/m)
  return d

def output(i, r, m, l):
  for t in range (1, l+ 1):
    print("month", t, "/lbalance: $", "{:.2f}".format(calculate(i, r, m, t)))

a, b, c, d = info()
total = calculate(a, b, c, d)
print("your investment is worth $", total)
output(a, b, c, d)

how do i do that? @CosmicBear

Don't say "it isn't working", tell what happened and what you wanted to happen.
You put everything in functions, but never ran the functions.