1. "When my c corp posts a loss, may I use my business expenses on my personal tax return as in home business expenses?"
No, you cannot use the C Corporation losses to offset your other income from your personal tax return. instead, the C Corporation losses are carried forward to the future years to be offset against any possible net profits earned by the Corporation. Unfortunately, this treatment is clearly not the same as losses earned from your home business.
2. When my c corp posts profits, do I use the deductions on my c corp 1120, personal (in home business) return or both?
The C corporation can only use the expense deduction incurred by the corporations to offset income earned from the corporation. The personal in home business expenses are not allowed to be used to offset the corporation income.