I moved from a 4000 square foot home in Colorado to a small condo in Hawaii last year. I only moved small items and limited amounts of clothing to Hawaii. I left my home in Colorado staged for real estate showings with most of my furniture and with a full garage. Due to work schedules and a the timing of closing on my home, I was not able to make it back to clear the home out before the new buyers took possession. I had very nice neighbors clear it out for me. I let them keep whatever they wanted in exchange for taking the rest to the local charity thrift store donation drop off. I have never donated more than $1000 in clothing or household items in the past. I estimate that I left about $15 thousand dollars (thrift store value) worth of stuff in the house. They did not get receipts. I have no concrete way to prove what was donated.
1. Can I estimate the value?
2. Can I enter all as one line item?
3. Will a sudden spike in my charitable giving likely trigger an audit?
If they didn't get receipts (which are required) and you can't prove what was donated, you're going to have to pass the deduction by because you need both.
You still have time to get a receipt/acknowlegement letter... As long as you have the receipt by filing time (April 18th this year, perhaps all the way to the last auto extension date - October), you can claim the deduction. There are some 'escape clauses' for donations of household goods when it's impossible for the charity to give you a receipt such as the Goodwill bin at the firehouse (or wherever), but claiming $15,000 this way would be suspicious at best.
Assuming you have a reasonably detailed list of what was donated, you probably can get your neighbor to take the list to the charity and get them to stamp it or whatever they do for donors and you should be set. Note that the charity will NOT value the items and it's now impossible to get a formal appraisal, which is required for 'donations of a group of similar items over $5000'. I'll leave it to you to figure out the grouping.