Don't start what you can not end.better tell them now that you don't want to be involving yourself in such act again,record it as you are telling them but get ready to face challenges from them,they can even sack you but there will be a reward for you one day and your integrity will speak for you.

Innobee99:
Bros, am talking about senior staff dat can sack and unsack here.....Am new here and scared of loosing my job.

but not scared of prison

You need to stop it now even you should have done that the first time. Just be very very polite and say sir/madam, pls don't be offended . I don't mean to disrespect you, just that I feel very uncomfortable after signing this. Pls I would not want to sign it again. Back it up with prayers and in the end you will be happy with yourself. Uphold your integrity.

Go to HR!They can re-organize job functions to block that loophole
and your own job also secured

Innobee99:
Pls i need a candid advise on how to deal with this situation at my work place.
I got this job August Last year after waiting for years after my NYSC. There is something going on here which is strictly against my believe and practice.
Some senior staff will come with receipts for me to sign. Receipts on goods and services that has not even taken place so that they can forward it to the headquarter for approval. How do i tell them its against my believe cuz i always feel that guilt after signing .
I need advise on how to go about it without offending anyone and without affecting my job.

Keep a record of ALL shady receipts they tell you to sign.

Record the date, the submitter, the vendor, the amount and maybe even take a picture of the receipt.

So the day anyone comes to audit or challenge you, you submit everything at once to the CEO without being asked. So it is clear you did it under duress and you are willing to help.