when trying to declare the IPUMS data as panel on stata there are repeated time values with id as serial no.

CPS
1

I use data from 1980 to 2017 for the month of March, for variables incomewage, education, occupation2010, union and states.

2

It sounds like you are trying to create a panel data set using SERIAL as your linking variable. As noted here, SERIAL is unique only to each household in a given survey month and year. Therefore, it sounds like you just need to identify the correct linking variable(s) for your analysis. Below is some information about linking household with IPUMS CPS data.

CPSID is an IPUMS-CPS defined variable that uniquely identifies households across CPS samples.

If you wish to link the March Basic samples to the March ASEC samples, you can use MARBASECIDP.

If you wish to link ASEC samples to other ASEC samples, you can use HRHHID with HRHHID2 for the years 2004-present and HRHHID prior to 2004.

I hope this helps.