I wouldn't exactly say 'not allowed'.. cos some do when pressured by the partner airline.

UA/AAs' FFP, I know do not charge fuel surcharge on partner airlines but will charge on their own metal.

AS's programme also does not charge for fuel surcharge on partner airlines but does on BA award flights only. That's why the people over at AS's forum are crying foul when they have to cough up over US$500 per transatlantic award ticket.

AC's programme only charges on some partner airines, ie LH, LX, TG but not SQ, OZ or NH

Outside North America, all programme charges for full taxes and fuel surcharges as though the 'free' ticket is a revenue ticket. So its not that they are 'crooks' as ajhira so kindly has said, but those are the general rules per programme.

I previously paid over US$500 for a BA J class ticket issued by BAEC routing HAM to CPT return via LHR (no stop). Same routing/flights issued by AA came out to US$100. Checking with Asiamiles, taxes about the same as BAEC.