[Pharaoh]

In general, ABSOLUTELY NOT!!!!

That being said, there are some limited cases. If the broker had a datafeed error, they may legitimately adjust some trades. This should be a very rare event.

If you did scalping or newstrading on a broker that specifically bans this style of trading, they can reverse those trades, but should delete both winning AND losing trades of that sort, if this is the case. Most brokers with this rule don't check very often and wouldn't be continuously adjusting your balance through the day.

After you close your last trade of the day, get a screenshot of your account history. Take another one each time your balance changes and compare them. This should show if they are modifying closed trades or doing something really strange.

It might also be a good idea to send them a note asking what's going on.

Please share what you find out - and the name of the broker if they can't fix the problem.