Well it is never actually posted - it is calculated dynamically each time you run the trial balance or balance sheet
the best documentation is the code see GLTrialBalance.php
Code:
if ($myrow['pandl']==1){
$AccountPeriodActual = $myrow['lastprdcfwd'] - $myrow['firstprdbfwd'];
$AccountPeriodBudget = $myrow['lastprdbudgetcfwd'] - $myrow['firstprdbudgetbfwd'];
$PeriodProfitLoss += $AccountPeriodActual;
$PeriodBudgetProfitLoss += $AccountPeriodBudget;
$MonthProfitLoss += $myrow['monthactual'];
$MonthBudgetProfitLoss += $myrow['monthbudget'];
$BFwdProfitLoss += $myrow['firstprdbfwd'];
} else { /*PandL ==0 its a balance sheet account */
if ($myrow['accountcode']==$RetainedEarningsAct){
$AccountPeriodActual = $BFwdProfitLoss + $myrow['lastprdcfwd'];
$AccountPeriodBudget = $BFwdProfitLoss + $myrow['lastprdbudgetcfwd'] - $myrow['firstprdbudgetbfwd'];
} else {
$AccountPeriodActual = $myrow['lastprdcfwd'];
$AccountPeriodBudget = $myrow['firstprdbfwd'] + $myrow['lastprdbudgetcfwd'] - $myrow['firstprdbudgetbfwd'];
}
}