Variable home loan interest rates will soon rise by more than the change in official cash rates, the Commonwealth Bank confirmed yesterday.The head of retail products in the Commonwealth's retail banking services division, Michael Cant, said: "It is inevitable that rates will reflect our funding costs. We are only being non-committal on the timing, the quantum and who goes first."Cant said the bank had already made some adjustments in its mortgage business to maintain margins. The number of honeymoon rates being sold has dropped by half since July.And the bank is pulling back on discounting. It has maintained its package offer, with a 70 basis point discount to the standard variable home loan rate of 8.57 per cent, but it has pulled back on the discretion available to loan writers to offer bigger discounts on large loans. Cant said the maximum discount, which was not disclosed, has been reduced by 10 basis points and was being offered on fewer deals.Cant did not say what sort of rate increase the bank was considering but the latest Reserve Bank statement on monetary policy offers some insight. The RBA said 45 per cent of business loans over $2 million are priced off bank bills.  Rates on such loans rose 15 basis points in August and a further 30 basis points over the following two months.Another 40 per cent of large loans are at variable rates and a sizeable proportion of those are also priced off bank bills. Rates on those loans are estimated to have increased by 35 basis points over the past three months.