Checklist for checking any birth chart
Before trusting any birth chart, check the inputs: the date, the local time, the time zone offset, the latitude and longitude of the birth place, and the ayanamsa used.
What it is
Check the time zone first, because India uses one offset for the whole country while other places may use different offsets or daylight saving. A wrong offset shifts the time by the same amount and can change the Lagna.
How it is worked out or read
Check the ayanamsa against the tradition you follow, and check the Moon's nakshatra against a printed panchang for the same date if you have one. A difference of about half a degree usually comes from the ayanamsa.
Where it appears on this site
The checklist and the method page list each step. The birth time article explains how small errors matter.
Inputs first
Before any reading, confirm the date, the local time, the time zone offset, the latitude and longitude of the birth place, and the ayanamsa. Each of these shapes the chart, and an error in any one can change the Lagna or the house of a planet near a boundary. Record the source of the birth time and how precise it is, since that determines how much weight the house-based results can bear.
Check the time zone with particular care. India uses one standard offset across the whole country, while places in other countries and some historical records use different conventions, and a wrong offset shifts every time by the same amount.
Calculation checks
Check the calculation against an independent source where possible. The Sun and Moon positions can be compared with a published almanac for the same date, and the nakshatra and tithi end times compared with a printed panchang. Agreement within a few minutes is expected, while larger differences usually come from the ayanamsa, the sunrise convention or the time zone.
Check the sign and house arithmetic as well. Count the signs from the Lagna to each graha and compare with the house the table gives. A counting error is simple to make and simple to find.
Interpretation checks
Finally, check the interpretation. State which rules were used and which sources they come from. Note whether a conclusion rests on one feature of the chart or several. Distinguish the calculated facts from the traditional readings, and say which of the two each statement is.
A chart reading that passes these checks is not guaranteed to be right, but it is open to examination, which is what a reader needs in order to trust it or to correct it.
What to do when a check fails
When a check fails, do not adjust the answer to match the expectation. Find the source of the difference first. The most common causes are the time zone, the birth time, the ayanamsa and a counting slip. Once the cause is found, correct it and repeat the calculation from the beginning, so that the final result is consistent with its inputs.