We have no fixed rules for express charges, but these normally apply to orders requiring a translator to work longer hours, to work overnight or over the weekend, or when running work on other projects has to be interrupted. In some cases, multiple translators have to work on a text simultaneously to meet the deadline.
You will be informed in any case IN ADVANCE if an express charge will be applied. This normally ranges between 25% and 50%, but can be as high as 100% in exceptional cases.