In a stock exchange notice yesterday (2 November), the trust said it was now "very close" to fully utilising its annual buyback authority and depleting its distributable reserves used for buybacks under its discount control mechanism (DCM).
"In addition, the board is currently exploring possible options for a combination with another investment trust, which would be affected by a scheme of reconstruction," it added.
Therefore, it said it would be suspending the DCM and the buyback of its shares.
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Peel Hunt analyst Thomas Pocock said that shareholders "will likely have expected better planning and communication", given that the seeking of additional shareholder approval and creation of appropriate reserves is possible in advance of them running out.
Pocock estimated the trust has bought back about £30m of shares in 2023, or 16% of shares outstanding.
He added: "Despite the possibility of a combination with another investment trust, given TIGT's 2% discount is already one of the tightest in the AIC UK Equity Income sector, we see little upside for shareholders and believe the DCM suspension may result in a meaningful short-term derating."
The board added that further details would be provided by the end of November, although "there is no guarantee that terms will be agreed".
"In the event that the board decides not to proceed with a scheme of reconstruction, it will provide a further update on when the DCM will recommence," it said.