Seeking Etiquette and Personal Finance Experts for splitting the bill

I’m seeking personal finance and etiquette experts to explain how to split the bill during romantic, professional and casual situations, particularly when using apps. How should one approach splitting an expense for: a meal or major purchase with friends, a significant other, or at work using apps like Venmo, PayPal, or Chase Quick Pay without sounding “cheap” or “rude”. (Not exactly my thoughts, by the way). Requirements: Must be either a Certified Financial Planner or an Etiquette Expert with experience with teaching others how to delicate professional and personal relationships. Responses must be detailed, and respondents must be available via phone on weekday evenings around 6 pm for follow-up questions.