Hello, Jono123, and welcome to the Grammar Exchange.
jono123 posted:"Your Youth Allowance has been cancelled from 1 January 2020 because we do not have income details for your parent/s."
I agree with you that the sentence in question has faulty grammar; the use of "has been canceled," which signals recent-past cancellation, conflicts with the use of "from 1 January 2020," which specifies a cancellation date in the near future.
You are right that the problem could be fixed by changing the present perfect ("has been canceled") to the future ("will be canceled"), but I recommend changing "from" to "on" and deleting "the" before the two dates:
- Your Youth Allowance will be cancelled on 1 January 2020 if we do not receive these details by 30 Dec 2019.
Another fix is to keep the present perfect but change "from" to "effective" and set the date phrase off with commas. "Effective" here relates to the phrase "the effective date," in this case, the date on which the cancellation takes effect:
- Your Youth Allowance has been cancelled, effective 1 January 2020, because we do not have income details for your parents.
What that sentence means, essentially, is that the allowance has already been cancelled in the computer system, but with the stipulation (or cancellation setting) that the cancellation not go into effect until 1 January 2020.