Is it true that if you were to work in a bank or an audit firm, you are technically not allowed to buy any stocks and shares in view of conflict of interest?

Yes it's stricter especially if you work in a financial institution. You'll need to declare any directorships or outside business interest and Compliance will need to assess whether there is a conflict of interest. Similarly for any shares that you own you'll need to declare upon joining, as well as every few months.

If you want to buy new shares, you'll need to seek pre-clearance (via a system) and if there's no conflict, it will be approved. Usually it will be approved qutite fast, unless there is a blackout period determined by the company. Abit more hassle but this is to prevent front running, insider trading etc. No workarounds to this unless you are not in this industry at all. Alternatively, speak to your Compliance to find out what are the exemptions. E.g. buying RSP probably only need to declare once, but don't need pre-clearance.​​​

As an ex-auditor myself, this is partially true. We are restricted to purchase shares in any of the audit clients, whether or not you are the one auditing them. And any shares you, your spouse, or your family members own in these companies needs to be sold. There will be checks carried out on a yearly basis to see if anyone is in violation of the rule, and if so there will be consequences. Independence is a huge and important matter in the audit industry.

For non-audit clients, we are not restricted from trading in their shares. However, if I'm not wrong, we would need to declare everytime we purchase or sell a share, so these additional admin matters usually put people off from active trading (besides the lack of time due to highly excessive workload).

Do take note though. I was in a situation once, where I bought a share in a non-audit client, only to see its price drop. Couple of months later, the company became our audit client and everyone in the firm were "forced" to sell at a loss. So best advice is, try not to trade when you are in an audit firm.