This depends on your account type.
EOD Challenge
Evaluation: none.
Funded: 2.5% of your starting balance, so $1,250 on a 50K, $2,500 on a 100K, $3,750 on a 150K.
1-Day-Pass-Plan
A daily loss limit applies in both phases, at the same percentage in each.
25K: 2.4%, which is $600
50K: 2%, which is $1,000
100K: 2%, which is $2,000
Instant Classic
3% of your starting balance, so $750 on a 25K, $1,500 on a 50K, $3,000 on a 100K, $4,500 on a 150K.
Instant Lite
25K: none
50K: 2%, which is $1,000
100K: 2%, which is $2,000
Flex Challenge
None, in either phase.
Daily Payouts
A daily loss limit applies in both phases.
25K: 2%, which is $500
50K: 2%, which is $1,000
100K: 1.5%, which is $1,500
150K: 1.5%, which is $2,250
What happens when you reach it
On every plan, hitting the daily loss limit is a soft breach, not a hard one. Your open positions are closed and the account is paused for the rest of the trading day. It resumes automatically on the next trading day, and the account is not closed.
Daily Payouts has one extra rule
If you hit the daily loss limit three times within any rolling 30 day period, the third hit is treated as a hard breach and your account is closed. See the Daily Payouts daily loss limit article for how the rolling window works and where to see your count.
Instant Lite also closes the account on a third hit. See the Instant Lite specifications for details.
For the exact figure on your account, check your dashboard.