Selected Answer

There are some relative references that must be made absolute.

[C8] =IFERROR(SUMPRODUCT('Drop offs'!$H$2:$H$849='Payment summary'!$B$4)*('Drop offs'!K$1='Payment summary'!C$3)+(SUM(IF('Drop offs'!**K2:K849**/'Drop offs'!$I$2:$I$849>0.99,1,0))),"0")

`=IFERROR(SUMPRODUCT('Drop offs'!$H$2:$H$849='Payment summary'!$B$4)*('Drop offs'!K$1='Payment summary'!C$3)+(SUM(IF('Drop offs'!K$2:K$849/'Drop offs'!$I$2:$I$849>0.99,1,0))),"0")`

[C9] =IFERROR(SUMPRODUCT('Drop offs'!$H$2:$H$849='Payment summary'!$B$4)*('Drop offs'!K$1='Payment summary'!C$3)+(SUM(IF('Drop offs'!**K2:K849**/'Drop offs'!$I$2:$I$849>0,1,0)))-C8,"0")

`=IFERROR(SUMPRODUCT('Drop offs'!$H$2:$H$849='Payment summary'!$B$4)*('Drop offs'!K$1='Payment summary'!C$3)+(SUM(IF('Drop offs'!K$2:K$849/'Drop offs'!$I$2:$I$849>0,1,0)))-`**C8**,"0")

Here, in addition, the reference to C8 is problematic. Try replacing it with *INDEX($A$5:$I$11, MATCH($A8,$A$5:$A$11,0),COLUMN())*.

[D16] =IFERROR(SUMPRODUCT('Drop offs'!$H$850:$H$2461='Payment summary'!$B$12)*('Drop offs'!L$1='Payment summary'!D$3)+(SUM(IF('Drop offs'!**L850:L2461**/'Drop offs'!$I$850:$I$2461>0.99,1,0))),"0")

`=IFERROR(SUMPRODUCT('Drop offs'!$H$850:$H$2461='Payment summary'!$B$12)*('Drop offs'!L$1='Payment summary'!D$3)+(SUM(IF('Drop offs'!L$850:L$2461/'Drop offs'!$I$850:$I$2461>0.99,1,0))),"0")`

[D17] =IFERROR(SUMPRODUCT('Drop offs'!$H$850:$H$2461='Payment summary'!$B$12)*('Drop offs'!L$1='Payment summary'!D$3)+(SUM(IF('Drop offs'!**L850:L2461**/'Drop offs'!$I$850:$I$2461>0,1,0)))-'Payment summary'!D16,"0")

`=IFERROR(SUMPRODUCT('Drop offs'!$H$850:$H$2461='Payment summary'!$B$12)*('Drop offs'!L$1='Payment summary'!D$3)+(SUM(IF('Drop offs'!L$850:L$2461/'Drop offs'!$I$850:$I$2461>0,1,0)))-'`**Payment summary'!D16**,"0")

You don't need to specify the Payment summary sheet when referring to another cell on the same tab. But the reference to D16 won't work and should be replaced by an INDEX/MATCH function as shown above.

I didn't test because I don't know what the correct results should be. I just picked off what appear to be obvious omissions and hope my effort helps.