I started my extremely small business officially (registered the name) in January 2015 but bought numerous pieces of equipment and supplies before that, in 2014 and 2013 (pro camera, sewing machines, small tools, materials - under $5000 worth of goods.) Is it possible to deduct these as startup costs even if they were purchased in previous years if I am currently in business? Could I deduct them on my 2016 taxes? Thanks in advance for any help!
Deductible items (small tools and materials) bought before your business opens are deducted (or amortized) as Startup Expenses when your business is 'open for business'.
Assets (generally items over $200 with a life of over one year) start to be depreciated starting when your business is 'open for business'. In some circumstance, you may qualify to increase that $200 amount to as high as $2500 (TurboTax will talk you through that in the "asset" section), in which case they would be Startup Expenses.
If your business was 'open for business' in 2015, that is when they need to be entered. You can not wait until 2016.
If the assets were not specifically purchased for business and/or has some personal use before they were used for business, you use the Fair Market Value when it was converted to business use, rather than the actual purchase price.