Two part comment below. Part #2 will be sent later
Part #1 (you working version) does not run when I "cut and paste".
If you have a working version that is running,
it would be better to analyze that for the problems you are having.
<html><head>
<script>
function $_(IDS) { return document.getElementById(IDS); }
function calculate_paid() {
var amtpaid = document.getElementById("amtpaid");
var rentdue = document.getElementById("rentdue");
var prevbal = document.getElementById("prevbal");
var hudpay = document.getElementById("hudpay");
var tentpay = document.getElementById("tentpay");
var datepaid = document.getElementById("datepaid");
var late = document.getElementById("late");
var paidsum = document.getElementById("paidsum");
var dateNow = new Date();
var dayNow = dateNow.getDate();
var datePaid = (dateNow.getMonth()+1)+"/"+dateNow.getDate()+"/"+dateNow.getFullYear();
datepaid.value = datePaid;
paidsum.value = parseInt(paidsum.value) + parseInt(amtpaid.value);
tentpay.value = parseInt(tentpay.value) + parseInt(amtpaid.value) - parseInt(hudpay.value);
if(dayNow > 5) { late.value = "L";}
}
</script>
<script type="text/javascript"> window.google_analytics_uacct = "UA-256751-2"; </script>
<script type="text/javascript"> window.google_analytics_uacct = "UA-256751-2"; </script>
</head><body>
.......
Some suggestions for above since
1. You define $_ but you don't use it.
2. Extra <script...> tags can be eliminated
For example, see modified code below:
<html><head>
<script type="text/javascript">
function $_(IDS) { return document.getElementById(IDS); }
function calculate_paid() {
var amtpaid = $_("amtpaid");
var rentdue = $_("rentdue");
var prevbal = $_("prevbal");
var hudpay = $_("hudpay");
var tentpay = $_("tentpay");
var datepaid = $_("datepaid");
var late = $_("late");
var paidsum = $_("paidsum");
var dateNow = new Date();
var dayNow = dateNow.getDate();
var datePaid = (dateNow.getMonth()+1)+"/"+dateNow.getDate()+"/"+dateNow.getFullYear();
datepaid.value = datePaid;
paidsum.value = parseInt(paidsum.value) + parseInt(amtpaid.value);
tentpay.value = parseInt(tentpay.value) + parseInt(amtpaid.value) - parseInt(hudpay.value);
if(dayNow > 5) { late.value = "L";}
}
window.google_analytics_uacct = "UA-256751-2";
window.google_analytics_uacct = "UA-256751-2";
</script>
</head><body>
.......
Note that the use of the [ code] and [ /code] tags (without the spaces)
maintains your formatting (if you had any) better than your first post.
I don't use PHP or mySQL, so I will be of no help concerning those aspects of your code.