I have been informed by my employer
that they do not have a specific date of which our salaries are paid, but I
quote: 'Usually we pay end of the month on a Thursday or Friday of that week'.
is not a custom I am used to and makes it extremely difficult to manage cash
flow. Are they legally able to do this?
When the salary needs to be paid depends on the type of contract you signed. If you are paid over a specific period standard rule is that the salary must be paid before the applicable period has ended. This means that if you are paid every month, your employer must pay your salary before the end of the month. So they can pay you even on the last day of the month. It is not required that you are always paid on the same day. Most employers however pay on the same day each month, but due to weekends and holidays the days may vary. In the employment contract it is even possible to agree that the salary is paid at a later date, for example at the end of the month following the month in which the work was done.
Answer is therefore that your employer is allowed to have the policy "to pay at the end of the month on a Thursday or Friday of that week".