MYOB's Invoice Payment system is a convenient way to enable customer payment by credit card or BPay.
MYOB charges a GST-inclusive fee of 1.8% of the total payment amount, plus $0.25 for each transaction.
At this stage the fee can't be directly charged to the customer so, if you want to recover it, you need to add it to the payment amount. The problem is that you need to know the total payment amount so you can work out the payment surcharge. So you keep going around in circles!
I took it upon myself to dust off my old high-school algebra skills and have arrived at a formula for you to work out the surcharge. (Yes, I'm still a nerd at heart.)
You simply take the GST-inclusive invoice total, multiply it by 0.01832994 and add $0.25. This amount includes GST.
E.g. a sale of $10,000 plus GST would take the invoice total from $11,000 to $11,201.88.)
MYOB calculates the surcharge as ($11,201.88 x 1.8%) + $0.25 = $201.88 incl. GST.
If you calculate the surcharge as a simple 1.8% of the GST-inclusive invoice total, that will often be close enough. The larger the invoice, the bigger the shortfall. For example, with the above sale of $10,000 plus GST, you would be out of pocket $3.88 incl. GST if you use the simple method.