After State Bank of Pakistan (the national treasury / federal reserve) has become an autonomous body, a letter of credit for import of goods can only be established only if the ITEM is in 'Approved List' for the foreign exchange control.
in nutshell if an LC has to be established for $5000 State Bank of Pakistan will only approve it at interbank rate at 100% +15% if there is equivalent Pak Rupees available in the business account.
The additional 15% is adjustable to cater for exchange rate fluctuation at time of document release.
what a f&%king mockery our banking system in country has become.
it may sound Portuguese to plenty of you but it is a fact, even after taking 100% away from account for exchange rate treasury want to hold addtional 15% to adjust incase of increment upon document retiring.
Just like after 100% payment for a car, we are charged additional when govt levy taxes and we have to pay before vehicle delivery.
@SER_GTR @chinyoti may be able to simplify it further