You are supposed to divide the internet between home and business use. That's why your accountant told you to take half - that's a safe number.
Then you - because you have two businesses - should be dividing the business portion by the two businesses that you have. If your wife's business uses it more than yours then it should definitely be placed in her deductions. But your business uses it too. Figure out the percentage and add some to yours and more to hers.
@Joor
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