Vastu beliefs restrict money transactions on certain lunar days, not just weekdays. Some Vastu guides tell people to avoid lending and borrowing on New Moon days.
These beliefs basically encourage people to plan their expenses carefully instead of handling money in a rush.
Important things you must know
These Vastu or astrology rules are just traditional beliefs. Science does not prove you will face a guaranteed loss if you transact on a specific day.
Therefore, you should never delay essential payments like emergency medical bills, school fees, house rent, EMIs, or bank transfers just because of a belief. You should make practical decisions based on your financial situation, payment deadlines, and actual needs.
In short: Some Vastu and astrology traditions ask you to avoid borrowing or lending on Tuesdays and Saturdays. You should understand this as a belief-based practice, not a strict scientific rule.