If Holdco is a connected corporation and is not the only shareholder that receives taxable dividends from Opco, Holdco’s Part IV tax would be a percentage of Opco’s dividend refund.
For example, let’s assume that Opco paid $6,000 of dividends to HoldcoA and $4,000 of dividends to HoldcoB. Upon paying these dividends, let’s assume that Opco receives a dividend refund of $3,833. The Part IV tax for HoldcoA would be $2,300 ($6,000/$10,000 * $3,833) and the Part IV tax for HoldcoB would be $1,533 ($6,000/$10,000 * $3,833).