http://jimbsail.info helps Skippers plan Europe Cruises
It is worth following JimB's advice and buying a few of those tax stamps at 88 euro cents. When the tax office is in a different town and several miles away it can cost much more the the 88 cents to get hold of one. We have also found Sundays can be a problem if the port police insist you have one and the office is shut.
The one time we were asked for the stamp was in Zea Marina when we foolishly did an unprompted change to the crew list. The port police had a nice little bit of paper with a map and Greek explanation of what we required for the tax office. After all this explanation, he then said there was no point in going as the office was on strike just then - would we please bring him 2 stamps when we were next passing through.....