Handler means that you are responsible for the purchase, including price and quality. More importantly, it means that you spent the money. Judging from the company's financial accounts, you spent the money.

Your department leader bought it himself and asked you to write a handling program, which itself shows that there is something wrong with this matter. If the amount is too large, I suggest you not sign it. You should be responsible for what happened. Of course, if the amount is relatively small, the things you buy will not have a great impact, and you can still sign for your future.