I've bought lots over the years from them personally, but not for any business purpose. The majority of items are sold by third parties who use AliExpress' marketplace, so you will need to contact the individual supplier in advance to ensure they can provide an invoice with the level of detail you require.
Depending on what you are buying and the quantities, there are some other sourcing sites that might work out a little cheaper, as AliExpress is quite consumer focused.