Cash to buyer if Seller Assist exceeds limit?

[Robin McMullen]

I've just sold a house in Pennsylvania and offered a seller assist of 3%. At closing, I was informed that the buyer's lender has a 2% seller assist limit. So the house sold for the original agreed upon price, however, the seller assist amount was 2% instead of the previously agreed 3%. After closing, my realtor, who is representing both buyer and seller, said that I need to pay that extra 1% in cash to the buyer. I understand how this works out math wise, however, there will be no documentation/receipt for this payment and that is making me feel uncomfortable. I'm concerned that I will be paying tax on this 1% since I assume that this would be considered a cash gift to the buyer? 

Thank you in advance for any advice on how I should respond to this situation