Could I confirm what you're saying: we don't need fill out the Cost of goods sold
True. Since your business does less than $1M of gross income a year, COGS is not required. But you can use COGS if you chose to do so. If you don't use COGS then you can enter what you pay for inventory as a supplies expense.
I myself use COGS for the sole reason that it allows me to more easily and simply keep track of inventory with each passing year. This way, I report my inventory on a first in/first out basis. Remember, since costs never stay the same what I paid for inventory purchased in 2017/2018 will most likely not be the same price I paid for that same inventory in 2019.
