Baptized brothers and sisters can handle the accounts for a congregation and perform the quarterly audit. I have actually seen this done. However, if there are sufficient elders and ministerial servants it is preferred to use them, even when their accounting skills are a complete ATROCITY. It twists my brain in knots because sisters would keep all the accounts straight and tied out properly.
Even Jesus appointed account servant was a freaking thief and a frugal grouch about the accounts.