It has to be fair to both parties, what if the purchaser refuse to buy? you hv the right to forfith the 3%.
In normal circumstances, letter of offer / Agreement to Purchase will hv specific performance once the vendor refuse to sign the S&P (refrain fr selling).
1. Purchaser has an option to :-
i) accept your 3% compensation (means you issue 4% and the agent refund the 2%)
ii) take legal action

2. Pay the agent the agreed professional fees. (2%)


In short you are facing 4 outcomes :-
a) Issue 4% to Purchaser (agent issue 2%) + issue 2% to agent as commission
b) Issue 4% to Purchaser (agent issue 2%) only - if the agent is kind enough not to take the commission
c) Just refund the 1% (agent issue 2%) to the purchaser and be prepare the purchaser take legal action on you
d) Just refund the 1% (agent issue 2%) to the purchaser + issue 2% to agent as commission, and be prepare the purchaser take legal action on you

p/s : Legal action can't be enforceable if agreement didn't states the SP