The two appointments reflect growing international involvement in Macedonia, where the five-month-old ethnic Albanian rebellion threatens to unleash all-out civil war.
The tax will go into effect on Sunday and extends to the end of the year, the state news agency MIA said.
It will be levied at the rates of either 0.5% or 1% on most private-sector transactions.
Correspondents say that Macedonia's impoverished economy has been further weakened by the costs of buying weapons for the army.
Fresh fighting
A recent lull in the fighting ended on Saturday with clashes between Macedonian troops and guerrillas on the slopes of the Sar Mountain near the border with Kosovo.
Diplomatic efforts to end the conflict continue.
The United States has appointed a Balkans expert, James Pardew, as its peace envoy to the former Yugoslav republic.
Mr Pardew is expected to work closely with his European Union counterpart, Francois Leotard, who was appointed earlier in the week.
The two appointments reflect growing international involvement in Macedonia, where the five-month-old ethnic Albanian rebellion threatens to unleash all-out civil war.
Mr Pardew has Balkans experience as a senior regional adviser at the US State Department, and was involved in negotiating a peaceful end to the conflict in Serbia's Presevo Valley, where ethnic Albanian guerrillas recently laid down their arms.
Mr Leotard, who arrived in Macedonia on Thursday, met President Boris Trajkovski for talks on the constitution on Friday.
Nato support
Nato on Friday gave final approval to a plan to send a 3,000-strong force to Macedonia, to help disarm ethnic Albanian rebels in case of a lasting ceasefire.
Nato spokesman Yves Brodeur said the alliance was ready to send the troops to Macedonia "provided the proper environment exists".
And the US State Department said Washington was prepared to offer logistical, medical and other support to the Nato force.