The proceeds you're describing could be fund expenses that required a return of principal payment. Look at your brokerage 1099 statement for another set of entries which have the same amounts except with negative values and with a description which says something like "investment expense". In this case my 1099 form includes the following footnote: "There are cases where the proceeds are used to pay expenses and there is no corresponding distribution.". In prior years these expense should have then offset the gain, but for 2018, as I understand it, Trust Expenses are miscellaneous itemized deductions which are not deductible by individuals. On my 1099 each proceeds entry includes an additional item called "Cost Basis Factor" and is a small decimal fraction. The full text of the footnote describing the proceeds in my case says:
This transaction represents the sale of assets from a Widely Held Fixed Investment Trust (WHFIT). The cost basis allocation factor is the value of the assets sold divided by the total net asset value of the trust. If you know your cost of the assets sold, use that to determine your gain/loss. Otherwise, determine your cost basis by multiplying your adjusted cost basis by the cost basis allocation factor. For example, if your adjusted basis is $1,000 and the cost basis allocation factor is 0.005 your cost basis allocated to that sale is $1,000 * 0.005 or $5. If there are subsequent sales of trust assets, your adjusted cost basis for the next sale is $995. Sales are reported based on when and for how much the trust sold the asset. This may differ both in timing and amount from what is distributed. There are cases where the proceeds are used to pay expenses and there is no corresponding distribution. For more information refer to regulations section 1.671-5.
The later regulation that is references is an IRS publication. Gads! What a hopelessly jumbled mess our tax system has become.
