The same positions, twelve different cuts

When two charts of the same moment disagree, it is almost never because the planets are in different places. Planetary positions come from the ephemeris and are not a matter of opinion: the Sun was at 11 degrees of Leo or it was not. What changes is where the lines dividing the wheel into twelve sectors are drawn.

Think of a plot of land: the ground is the same and the boundaries can be laid out in several ways. Each house system is a different way of laying them out. None of them is the true one, so the point is not to pick the correct system but to know which one was used.

Placidus divides time rather than space. It takes the arc each degree of the zodiac needs to climb from the horizon to the midheaven and cuts it in three. It has been the most widespread system in modern Western astrology since the seventeenth century, and it is what most software opens with.

It has a known physical limit: above the Arctic Circle some degrees never rise at all, so the division becomes impossible or meaningless. For a birth that far north, another option is worth considering.

In whole signs the ascendant's sign is the entire first house, 0 to 30 degrees, and every sign after it is a house. There are no intermediate cusps, no intercepted signs, and no latitude that breaks it.

It is the system of Hellenistic astrology, the one in use through most of the first millennium, and it has come back strongly. Comparing your chart in Placidus and in whole signs, some planets change house: that is exactly what should happen, not anyone's mistake.

Koch divides using the latitude of the birthplace as its reference and became popular in German-speaking astrology. Regiomontanus divides the celestial equator and was the medieval standard, the one horary charts were cast with for centuries. Equal houses draw exactly 30 degrees from the ascendant: it keeps the ascendant and gives up on the midheaven being the cusp of the tenth.

All of them answer the same question with different geometry. None is an improved version of another.

A printed chart that does not declare its house system is a drawing nobody can check. Someone reading it in ten years will not know which convention they are looking at, and a different house can change the reading of a planet entirely.

So the certificate that ships with every order states the system used, along with the resolved coordinates and the time zone. It is not packaging: it is the only way the piece stays verifiable once we are no longer standing next to it explaining.